Siege of Humaitá

Siege of Humaitá
Part of the Paraguayan War
The allies resort to balloon observation to pick their way through the wetlands of southern Paraguay — the first use of aviation in South American warfare (Sketch by American balloonist James Allen, 1868)
Date 22 July 1867 – 26 July 1868 (1 year and 4 days) Location Floodplain of the Paraguay River, near present-day Humaitá, southern Paraguay 27°4′12″S 58°30′0″W / 27.07000°S 58.50000°W / -27.07000; -58.50000 Result Allied victory
Belligerents
Paraguay	Argentina Brazil Uruguay
Commanders and leaders
Solano López Paulino Alén [es] Francisco Martínez	Bartolomé Mitre Marquess of Caxias
Strength
At the beginning:[1] 20,000 ~400 guns At the end:[2] 1,324	At the beginning:[3] 40,000 Brazilians 4,000 Argentines 600 Uruguayans
All numbers should be received with caution since 19th-century official military reports were often intended for public consumption, so potentially may feature inflated or decreased values.

The siege of Humaitá was a military operation in which the Triple Alliance (Brazil, Argentina and Uruguay) flanked, besieged and captured the Fortress of Humaitá, a Paraguayan stronghold that was referred to as the Gibraltar of South America. It fell on 26 July 1868. It can be considered the key event of the Paraguayan War since the fortress had frustrated the allied advance into Paraguay for more than two years. However it did not surrender as the defenders escaped, most of them to fight another day.

The allies were severely criticised for the time it took them to take the installation, whose strength was belittled. But they were essentially a pre-professional army fighting a long way from home against an unaccustomed defence tactic: artillery in prepared, entrenched positions firing a hail of anti-personnel shot. Further, they were battling in unprecedented terrain — most of it impassible, all of it unmapped — in the wetlands of southern Paraguay. It gave the Paraguayans, who fought with exemplary courage despite being abysmally supplied, a huge advantage.

Moreover the allies, who at first had attempted to take the fortress by frontal attack from the Paraguay River, had instead suffered a catastrophic defeat; this had disorganised and demoralised their forces. Restoring their military effectiveness was a task that fell on the shoulders of the new commanding general the Marquess of Caxias. For political reasons he could not risk another disaster.

The Paraguayan war was one of the major conflicts of the 19th century, and far and away the most lethal in the history of South America. Yet it is little known outside that continent.^[4] It had three phases:

1. Paraguay declares war on Brazil and Argentina — countries vastly more populous than itself^[5] — invading three of their provinces.^[a] The two countries, plus Uruguay, sign the Treaty of the Triple Alliance, vowing never to lay down their arms until they have toppled Paraguay's leader Francisco Solano López.
2. The Allies invade Paraguay, and at length capture its capital Asunción;
3. Guerrilla warfare and the pursuit of López, who is finally killed by Brazilian cavalry after refusing to surrender.^[6]

Its key event^[b] was the capture of the Fortress of Humaitá, which was the gateway to Paraguay, and had held up the allied advance for over two years.^[7]

• 
  Location in heart of South America
• 
  Context: wetlands of southern Paraguay

The maps show why the fortress was the key to Paraguay. The country is landlocked, but can be accessed from the sea; one must sail up two of South America's great rivers in succession:

• The River Paraná, which traverses many miles of Argentine territory. (A small portion of the Paraná is visible at the bottom of the Context map, marking the boundary between Argentina and Paraguay.)
• The River Paraguay, the country's principal highway,^[8] and after which it is named.

As shown, Humaitá was a few miles up the river Paraguay. At first it was just a modest guardia or lookout point manned by a few soldiers.^[9]

In the 1850s there had been two separate incidents in which Paraguay had been threatened by the naval flotillas of irate foreign powers, namely Brazil and the United States.^[10] It became apparent that warships, though based in the Atlantic Ocean, could steam up into Paraguay quite rapidly.^[11] Thus, the transition from sail to steam made the Paraguayan government realise that, far from being secure in the heart of South America, it was vulnerable.^[12]

Accordingly, the Paraguayans had greatly strengthened the fortress of Humaitá. Its purpose was to bar the way in to Paraguay. Commanding a hairpin bend in the river, it had a formidable reputation.^[c]

For the Brazilians the fortress was doubly vexing. It blocked the river route to their province of Mato Grosso, which lay hundreds of miles upstream, and had been occupied by Paraguay since the war began. It was by far the most convenient means of access to their territory,^[13][14][15] a land about the size of Germany. Unless they got past Humaitá there seemed little prospect of recovering it.^[16]

Hoping for a quick result, the Allies tried to take the fortress by frontal assault from the river Paraguay.

On 22 September 1866 they landed troops on the edge of the only substantial piece of firm ground, a meadow marked M on the map Terrain. To attack in that place was a rational decision in itself, for they had hit upon a weak spot, and they might well have prevailed, greatly shortening the war. But their commands were divided, they dithered and delayed, and the Paraguayans built a defensive earthwork in the nick of time.^[17]

Armed with artillery firing a hail of grapeshot and canister,^[18] it destroyed the allied attack; many Argentine and Brazilian soldiers, advancing over open ground, were killed.

The Paraguayans, staying behind their defences, had few losses.^[19]

This was the battle of Curupayty, the allies' first major setback, and their worst defeat of the war.^[20]

Thus, the allied armies, having landed in Paraguay, controlled only 9 square miles (2,330 hectares) of its territory:^[21] inhospitable wetlands. Their advance was stymied by this seemingly invincible fortress; and, as will now appear. they were thoroughly demoralised.

The allied advance into Paraguay came to a complete halt after the disaster of Curupayty.^[22]

The defeat caused dissension among the allied commanders and no one knew what to do next.^[24]

After the battle, Joaquim Marques Lisboa, the Viscount of Tamandaré and commander of the Imperial Brazilian Navy, Polidoro Jordão, commander of the 1st Brazilian Army Corps, and Venancio Flores,^[25] commander of the Uruguayan army, left their positions.^[26] Tamandaré was replaced by Joaquim José Inácio^[26] and Flores was replaced by Enrique Castro; according to historian Thomas Whigham, Uruguayan participation in the war was now reduced to a "token force only nominally Uruguayan in composition".^[22]

The question of who should lead the Imperial forces remained however.^[27] In Brazil, emperor Pedro II was determined to continue the war despite Curupayty; the new cabinet, headed by prime minister Zacarias de Góis e Vasconcelos, of the Progressive League, which rose to power seven weeks before the battle, was tasked with continuing the war.^[28]

The emperor then nominated an experienced and prestigious general to lead the Imperial forces in Paraguay: Luís Alves de Lima e Silva, then Marquess of Caxias, by a decree on 10 October 1866.^[29][27][30] The decree did not give Caxias command of the Brazilian navy; thus on paper it did not unify command of the Brazilian land and naval forces; despite this, the navy also fell under Caxias' command, and would no longer operate separately as it had done since the start of the war.^[31] There was a concern on the part of the Brazilian government not to leave the navy under Argentine president Bartolomé Mitre's command.^[30][32]

Caxias took his first steps by creating the 3rd Army Corps in Rio Grande do Sul already on 18 October 1866, while still in Rio de Janeiro.^[33] He departed aboard the steamer Arinos on 29 October 1866, stopping at Montevideo on 2 November, Buenos Aires on 6 November, Rosario on 9 November and Corrientes on 14 November, finally reaching the allied camp in Tuyutí on 18 November. Upon his arrival, he issued his Order of the Day No.1, in which he stated to the troops that "if I didn't already know you, I would recommend you valour; but in the countless battles that have taken place to date, you have given ample proof of this military virtue"; the next day he assumed unified command of the 1st and 2nd Brazilian Army Corps.^{[26][34][35][36]}

At that point several diseases had spread in the battlefield, but a new cholera outbreak proved worst, killing or incapacitating thousands of soldiers;^[37] the cholera epidemic became so serious that the Allied commanders tried to disguise it from both the Paraguayans and the civilian population in their respective countries, even prohibiting the use of the word "cholera" in official communications.^[38] By March 1867 the epidemic had spread to Buenos Aires and Montevideo.^[39] Less than a year later, on 2 January 1868, the illness was to kill Argentine vice-president Marcos Paz.^[40]

The military camps did not follow basic hygiene practices and were filthy and disorganised.^[41] The soldiers often drank contaminated water, which they got by excavacating the nearby sandbanks; the water was contaminated by dead bodies that were frequently buried near the water sources.^[42] In order to cool a demijohn of water, the soldiers would dig a hole in the ground and bury it. Dionísio Cerqueira [pt], a Brazilian soldier, later recalled, after having ordered a hole to be dug in his tent, that "as soon as the comrade had reached the bottom, we felt the characteristic smell of death. One more hoe hit and a rotten skull appeared. He plugged the hole and dug another one ahead".^[43]

The sanitary conditions were not the only issue, for the organization and morale of the allied army were also abysmal.^[44] Referring to the state of the 1st and 2nd Brazilian Army Corps, Caxias later stated that "they seemed to belong to two different nations", as each had their own administration, accounting, payment and promotion criteria.^[45][26][46] This was also a problem in other units, especially the corps of Voluntários da Pátria (patriot volunteers).^[46]

Another issue was the general lack of materiel: the cavalry was short of horses and those it had were poorly fed;^[47] the 2nd Army Corps, for example, was completely dismounted;^[46] many soldiers had traded their uniforms and walked half-naked or barefoot; the Minié rifles used by the infantry needed a ramrod to function, many of which had been damaged; the artillery lacked heavy calibre guns, something that some observers pointed out as one of the causes for the allied defeat at Curupayty; there were also no ox carts or oxen to transport goods and troops.^[46][48]

Ever since the signing of the Treaty of the Triple Alliance the commander-in-chief of all the allied forces had been Argentine president Bartolomé Mitre. After Curupayty, Mitre's prestige fell and growing 'federalist' rebellions in Argentina, headed by armed bands called montoneras, forced him to pay less attention to the war against Paraguay; this also meant that an increasing number of Argentine soldiers had to be diverted from the war to quell the rebellions in the Argentine interior, the most notable of which was led by Felipe Varela [es], a federalist and staunch opponent of Mitre, Brazil and the war against Paraguay.^[49] The political implications are described further below. For the Argentine federalists, Brazil was an enemy ever since its role in defeating Juan Manuel de Rosas during the Platine War fifteen years earlier.^[50]

In November 1866, 1,000 Argentine soldiers left the allied army and marched to Buenos Aires in order to join troops being raised there to put down the rebels; Mitre appointed general Wenceslao Paunero to command this army, but its effectiveness was limited and the rebellion continued; on 24 January 1867, 1,100 more Argentine soldiers were detached from the Allied army and sent back to Argentina in order to join Paunero's army; then, the Argentine president himself embarked on a steamer on 9 February 1867, heading back to Argentina with another 3,600 soldiers and leaving only four thousand Argentine troops in Paraguay under the command of general Gelly y Obes.^[51]

Command of the allied army now de facto rested in Caxias' hands, who assumed it provisionally after Mitre's departure; such a reduced number of Argentine soldiers left in the front also meant the allied army strength now depended mostly on Brazil.^[45][52] By April the rebellion was defeated; the rebels had received considerable aid from Chile, but could not resist the government force sent against them.^[53] Mitre returned to Paraguay in July 1867, technically reassuming command of the Allied army, though Caxias continued to exercise extensive authority.^[54]

The precarious state of the troops made a deep impression on Caxias, who concluded that serious measures were needed to make the army operable and continue the campaign.^[55] The marquess later stated, after his return to Brazil, that "it was therefore necessary to call in everything, carrying out a new reorganisation and, for all of that, time was indispensable".^[56] Caxias then set out to reorganise the army, step by step, gradually improving its morale, discipline and hygiene.^[55] He took several months to reorganise and stabilise the front before deciding to resume allied actions; this made him a subject of mockery and criticism in the Brazilian press, which did not understand the issues surrounding the theatre of war.^[24][26]

Caxias' first measures upon assuming command applied to hospitals, ambulances, uniforms, food and transportation. He started to reorganise the Brazilian Army's depots in Argentina and Uruguay and the health service since his departure from Brazil.^[26] The Brazilians had eleven hospitals in the region, four of which were in Paraguayan territory and all of which were overwhelmed by a large number of patients.^[45][57] The allied army was in complete disarray. According to Francisco Doratioto, a third of the initial Brazilian force that had crossed the Paraná River into Paraguay was either sick or wounded by the time of Caxias' arrival, despite having received reinforcements.^[45]

A medical commission led by Francisco Pinheiro Guimarães, a physician and colonel of Voluntários da Pátria who had already dealt with epidemics in Brazil, was nominated by Caxias to inspect the hospitals.^[45] Guimarães isolated the cholera patients and instituted strict sanitation standards.^[58] Caxias himself was meticulous in his habits, only drinking mineral water brought to him from Rio de Janeiro and ordering his quarters to be cleaned daily.^[59] One of the goals of the commission was to inspect the hospitals to search for soldiers that were no longer sick and were overstaying with the doctors' connivance; fifteen days after the commission's creation, some twenty to twenty-five hundred soldiers were sent back to Tuyutí for active duty.^[45][58]

In order to deal with the precarious state of the camps, Caxias also convened all division and brigade commanders for a meeting in which it was decided to create a Field Police Inspectorate. This unit would be responsible for inspecting whether the officers were following the organisation and sanitation norms or not.^[60][61] The police inspectors' duties required them to be zealous for the camps' safety and order; for example, they included "not allowing games, gatherings, or disorder, and to patrol areas, especially the sutlers' districts'; and "list all existing female camp followers and make them rush to the hospitals as soon as the battle begins".^[62] According to Aureliano Moura, this unit was the precurssor of what would later be the Brazilian Army's Police.^[63] The marquess himself adopted the custom of making frequent morning visits to the brigades; in these visits he inspected the camps and the soldiers, paying close attention to their armament, uniforms and training.^[64] Officers were often punished for sloppiness with the smallest details; some were even arrested.^[65]

Parallel to the sanitation improvements, the marquess also reorganised the army. Caxias began by making changes to the army's administrative structure on 22 November by Order of the Day No. 2, merging several administrative divisions and creating others. He extinguished the post of chief of staff in the 1st and 2nd army corps while keeping it in his headquarters, along with two assistants, three engineers, four aides-de-camp, some officers and amanuenses. The next day, by Order No. 3, he started to reorganise the troops.^[55] The units of Voluntários da Pátria were a great problem, for they were not standardised, with a varying number of companies and soldiers in each unit; on 20 December, they were restructured, with each one being assigned six companies.^[66]

In addition, Caxias was also concerned with the tactics and procedures adopted by the troops in battle; he banned the use of any occupation badges in combat and reconnaissance missions, ordering the officers' kepi to be covered with a white tissue, similar to what the soldiers used; this demonstrated his willingness to set aside the old aristocratic pageantry if it interfered with the war.^[34][61] During his routine visits, the marquess noticed that some officers were not following the battle formations provided for in the military regulations in effect at the time, especially the formation of squares against cavalry;^[67] Order of the Day No. 5 had determined that whenever the infantry formed squares, it should do so in four rows.^[61] Up until that point, new recruits were immediately handed guns and sent to battle, which could endanger the entire Allied army; to tackle this issue, from 7 December onwards all new recruits were given a fifteen day training on battle maneuvers and marching before being handed guns.^[64]

The materiel deficiency was also remedied. The marquess convinced the imperial court in Rio de Janeiro to buy five thousand modern breech-loading Roberts and two thousand Spencer repeating rifles from the United States.^[24] In order to teach the soldiers how to use the new breech-loading guns, Caxias ordered the 1st Army Corps to select 25 men who would be taught how to use them and then spread the knowledge to the rest of the troops.^[66] An intense movement of provisions took place, with horses and mules being bought to be used in combat and in the transport of goods; the animals began to be fed alfalfa and corn, proper food that prevented them from falling ill.^[68]

Caxias took fourteen months to implement these measures.^[68] The results of his efforts were notable. The traveller Sir Richard Burton visited a Brazilian camp near Humaitá in August 1868 and was impressed by its hygienic cleanliness and how well the soldiers were sheltered, clothed and fed.^[69] "Before he took charge, the Brazilian army was in the worst possible condition; now it can compare favourably as regards the appliances of civilization with the most civilized".^[70]

The plan that was to lead to the capture of Humaitá was as follows. Instead of attacking it frontally, it was to be broadly encircled from the rear and taken by siege. This required two operations, military and naval.

Allied troops, starting from their existing point of concentration — their base camp near the mouth of the river Paraguay — were to effect a flanking march well to the landward side of the fortress, giving its outer defences a wide berth, then marching to rejoin the river wherever it was convenient to do so. Thus the fortress would be cut off by land.^[71]

But, though isolated by land, of course the Paraguayans would have continued to resupply the fortress by river, so it was necessary to cut it off by water too. Therefore the plan called for armoured Brazilian gunboats to force their way past Humaitá's batteries and deny the river to Paraguayan vessels. As explained in the article Passage of Humaitá, this was much easier said that done.

The plan had been proposed by Mitre and readily agreed by Caxias. (Long after the war, though, partisan Brazilian and Argentine journalists sought to belittle Mitre or Caxias and give sole credit to the other man.)^[72]

When this plan was conceived the allies did not know where the river could be rejoined, since the local topography (carrizal, see below) makes this impossible in most places. Indeed López and his entourage came to believe the crucial information (that the river could be rejoined at a place called Tayí), and even the plan itself, was given to Caxias by a small group of Paraguayan defectors, including López's two brothers, Benigno and Venancio, the U.S. envoy to Paraguay being another one of the alleged conspirators.^[73]

Implementation of the plan was nearly obstructed by the Brazilian navy, which refused to take orders from Mitre. Even after Caxias assumed supreme command they were very reluctant to proceed until forced into a corner, behaving heroically, though, when it came to the point.^[e]

The map shows the simple concept. In practice there were formidable difficulties to overcome.

Some foreign observers bitterly criticised the allies for the slowness with which they captured the fortress. It was even implied that corrupt motives might have to do with it.^[74][75] In recent times some conspiracy theorists have reasoned that it was done deliberately as part of a Final Solution to exterminate the Paraguayan race.^[76] Even Caxias himself, before he was given sole responsibility, grumbled that Mitre was in no hurry to get on with the war because Argentina was getting rich from it.^[77]

The serious practical difficulties faced by the allies — who were operating without the benefit of hindsight — should therefore be described.

Brazilian troops, artillery, ammunition and stores had to be brought to the vicinity of Humaitá from Rio de Janeiro by steamship: a 1,500 nautical mile (2,778 km) journey down the Atlantic ocean and up again through the rivers Plate, Paraná and Paraguay that took about a fortnight.^[f] Thus ocean-going ships had to steam up the Paraná river, where they risked running aground on its frequent sandbars.^[78] The alternative, the overland route from Brazil to Paraguay was so bad that it was attempted only once, with disastrous results.^[79]

Cavalry horses and draught animals died from eating "a poisonous herb called 'mio-mio',^[g] which abounds in the South of Paraguay, and which only animals reared in the district have the instinct to avoid".^[80] Hence fodder had to be imported from downriver Buenos Aires or Rosario, its price rising to £8 gold^[h] per ton. According to Richard Burton, who visited the scene, "It was terribly wasted by exposure to wind and weather, and in places I have seen it used to bridge swamps. This unexpected obstacle added prodigiously to the difficulties and expenses of the invader".^[81]

The sea and river journey, though long, could be said to be the easy part. Cargoes were landed at Paso de Patria or Itapirú in southern Paraguay and had to be taken to their final destinations by mule cart. Convoys left once every two days and threaded their way through the marshlands.

By the time the allies had encircled the fortress, rejoining the river at Tayi, the route was many miles long. Those who went on it were liable to be ambushed and harassed by Paraguayan forces.^[82]

When eventually the Brazilian armoured gunboats did dash past Humaitá and remake contact with the encircling land force they had to be resupplied via this tenuous route. According to George Thompson

The Allies had to transport overland to Tayi all supplies and ammunition for their ironclads. They had to pay £2 10s for the transport of a 150-pounder shot, and £33 [say, $5,000 today] for the carriage of a ton of coal.^[83]

Hence this vital line of communication — it was 70 km long^[84] — might conceivably have been cut at any time if the Paraguayans had been bold and fortunate.

To appreciate the wetlands terrain of southern Paraguay — where the allies were bogged down in an area of only a few square miles — it helps to understand some peculiarities of this portion of the river, called the Lower Paraguay.

The Lower Paraguay has a channel that is about 2,000 feet (600 metres) wide on average; it has a meandering pattern with an irregular and complex water regime. Its hydraulic gradient (mean slope) is very small (2 cm/km). When the water is high it cannot discharge into the Paraná fast enough: it backs up and causes extensive flooding. Not far above Humaitá it receives an enormous streamload of sediment, a mud brought from the slopes of the Andes by a tributary, the Bermejo River.

Thus, the Lower Paraguay is characterised by sediment erosion in the main channel and deposition in its floodplain channels. Although its left (eastern) bank is elevated, both banks are overflowed during the winter floods, as shown in the photographs from space, forming "meander scroll remnants, shallow lakes, ponds, marshes and long and narrow scroll-swamps"; the floodplain is poorly drained.^[85] The local topography is continually changing, differing in summer and winter, and even from year to year.

Viewed from space

Confluence of the meandering River Paraguay, above, and River Paraná, centre, coffee brown. (Goddard Space Flight Center)

Lower Paraguay floodplain. Notice terrain (somewhat drier nowadays — there are even some roads). Present-day Humaitá, a small town, is under tip of hairpin bend (Johnson Space Center). Compare with Thompson's 1869 Terrain map below.

Once the Paraguayans had denied access to the meadow M at Curupayty, there were few pieces of firm ground upon which the allied troops could manoeuvre. Most of the surrounding terrain was almost impassible, and consisted of the following features; they were described by George Thompson, chief engineer of the Paraguayan army.

Carrizal. Extending from the river bank and up to three miles inland, it was land intersected by deep lagoons and deep mud, "and between the lagoons either an impassable jungle or long intertwined grass three yards high, equally impenetrable. When the river is high, the whole 'carrizal', with very few small exceptions, is under water, and when the river is low, and the mud has had time to dry, paths may be made between the lagoons".^[86]

Esteros. Basically lagoons choked with stiff, gigantic aquatic plants, they surrounded the Paraguayan positions and formed their principal defence. "The water of these 'esteros'... is full of a rush^[i] which grows from 5 to 9 feet above the level of the water. The water in all standing ponds, is full of this rush..." These plants, called pirí, were triangular in section and grew perfectly straight.

These rushes grow about two inches apart only, and are consequently almost impassable in themselves. The bottom they grow on is always a very deep mud, and the water over this mud is from 3 to 6 feet deep. The 'esteros' are consequently impassable excepting at the passes, which are places where the rushes have been torn out by the roots, and sand gradually substituted for the mud at the bottom. In these passes, as in the rest of the 'esteros', the depth of water to be waded through is from 3 to 6 feet. In some places, one or even two or three persons, on very strong horses, can pass through the rushes; but, after one horse has passed, the mud is very much worse on account of the holes made by the first horse's feet.^[87]

The Chaco. On the opposite shore of the river began the Gran Chaco, a region so inhospitable it was never conquered by the Spanish Empire. Claimed by both Argentina and Paraguay, it was still uninhabited, except by the feared Toba people and other indigenous.^[88] The coastal region was almost impassible.^[89] Eventually, pressure of war obliged both sides to make quite extensive forays there; see below.

The allies had no experience of fighting or manoeuvring in terrain such as just described. Open, mobile warfare was the preferred style in South America where wars were quick and decided through pitched battles.^[90]

Both sides learned the folly of attack over open ground, the Paraguayans at the Battle of Tuyutí and the allies at Curupayty. Around Humaitá "there was a conglomeration of lagoons, marshes and patches of jungle connected by narrow strips of terra firma which the attacking side had to squeeze through on a narrow front": this conferred a huge advantage on the defence.^[91]

A simple defence tactic was employed which was unusual in South America.

"The Paraguayans had not many infantry, and they relied most on their artillery in case of an attack", said their chief engineer. The artillery would fire grapeshot or canister — a hail of small shot which was a crude predecessor of machine-gun fire. While this was commonplace in itself, what was unusual was its deployment from earthworks.

The earthworks were made by digging a ditch about 12 feet wide and 6 feet deep (~ 4 x 2 m). The soil was used to construct a thick parapet. The defenders sheltered behind the parapet and so the attackers had to cross the ditch before they could climb it. As practised in Paraguay the slope of the ditch and the parapet were made continuous; this made it particularly tall and hard to climb. Soil with such a steep slope will collapse e.g. as soon as it rains^[92] and so it was revetted with thick sods cut from the grass-covered earth. To some extent this lining was fractured by enemy artillery rounds but turf in Paraguay was much harder than in Europe.

Infantrymen on the firing step fired at the enemy over the parapet. Small salient angles were made to allow the artillery guns to project forward, or they were raised on platforms to fire over the infantrymen's heads. Such an arrangement (en barbette) demanded courage from the artillerymen because they were unprotected, but on the other hand gave them the widest possible field for action. By resting the ends of the earthworks on the esteros or other impassible terrain they could not be flanked.^[93]

As to the strength of such defences, cadets at West Point were taught general Horatio Gouverneur Wright's maxim: "A well intrenched line, defended by two ranks^[94] of infantry cannot be carried by a direct attack".^[95] (When the use of defensive earthworks had been resorted to in the Great Siege of Montevideo — the nearest precedent — it had baffled the attackers for 8 years.) As will be described, four times a direct attack was tried in this campaign. The attacker casualties were enormous and it did not work except against heavily outnumbered defenders.

When an army faces an unprecedented situation much depends on the professionalism of its officer corps. "Until 1865, the Brazilian army was essentially pre-professional", wrote American scholar William S. Dudley: its officer corps did not awaken to the need for modernisation and renewal until after the war.^[96][97] For Leslie Bethell, a modern, professional army was created by Caxias only in the course of the campaign itself.^[98] The Argentine and Uruguayan officer corps certainly were not better prepared since, unlike the Brazilians, they did not even have an adequate supply of military engineers.^[99]

While the Paraguayans were familiar with the ground, maps of the territory were, for the allies, non-existent. At first completely ignorant of the terrain, they did not even realise that Humaitá was protected by miles of earthworks.^[100]

The allied base camp was frequently harassed by Paraguayan snatch squads that used to kidnap the sentries (see below). The allies did not realise why: they had placed their camp right next to a corner of the Humaitá trench works: the el Sauce corner. It was hidden from them by the thick vegetation.^[j]

There being no maps, they had to be created. The Brazilian cavalry frequently went out to reconnoitre but this branch was adapted for relatively open ground. At ground level men could not see far because of the vegetation. Two other methods were resorted to.

These were improvised watch towers. Richard Burton saw and described them;

The rough contrivance, varying from forty to sixty feet in height, is composed of four or more thin tree-trunks, planted perpendicularly, and supplied with platforms or stages of cross-pieces, mostly palms, the whole being bound together with the inevitable raw hide. The look-outs are ascended by notched palm-trunks, or ladders, which, after a little neglect, become dangerous... In so flat a country the mangrullo acts well.^[101]

In August 1866 the Polish engineer Robert Adolf Chodasiewicz [pl] of the Argentine army, who had acquired his skills in the Crimean War, had made a preliminary map of the area south of Humaitá; he did so by triangulating from three mangrullos.^[102]

Chodasiewicz added further refinements after the battle of Curupayty. With the consent of Caxias a copy of his map was given to Charles Washburn, the American envoy to Paraguay, who was passing through the allied lines, knowing Washburn would show it to Francisco Solano López. López was impressed by its accuracy and became convinced there was a traitor in his ranks who had sold the information to the allies. Suspicion fastened on his brother Benigno; in 1868 he was shot for treason.^[20]

On the initiative of the Emperor Pedro II himself and the War Minister João Lustosa da Cunha Paranaguá, Marquess of Paranaguá,^[103] the Brazilian government contracted the Allen brothers, veteran balloonists of the American Civil War, to establish a balloon surveillance unit. They were recommended by Professor T. S. C. Lowe, formerly chief aeronaut of the Union Army Balloon Corps.^[104] The brothers imported two balloons. These had cotton envelopes, which were varnished to make them gas-tight, and were filled with hydrogen, which was made by mixing iron filings with sulphuric acid. It was the first time aviation was used in South American warfare. The balloons did not fly freely: they were tethered by manilla ropes and could be maneouvred by teams of 30 men trained for the purpose.

To the exasperation of Caxias the iron filings had not been despatched from Rio de Janeiro, so lump iron had to be substituted; hence the apparatus would not generate very much hydrogen. In consequence, ballooning was delayed, and the larger balloon, which could have carried more observers, was not used at all.^[105] The smaller balloon had a diameter of 8.5 metres,^[106] or 9 metres, according to another source.^[107]

The first ascents were made in June and July 1867. In the second of those the balloon rose to 400–450 feet (120–130 m) and stayed up two hours. In the basket were Chodasiewicz and a Paraguayan scout. Recalled the Pole:

With the aid of a long distance eyepiece we could make out — for the first time — all those formidable lines of fortifications. We saw the whole Paraguayan Quadrilateral; its el Sauce corner, concealed in the jungle, bang in front of our army's extreme left ... also its SE corner redoubt united with Humaitá's [inner] trenches^[107]

Barely a fortnight after this ascent, Caxias began his great flanking march.^[108]

Although Caxias used the balloon again on his flanking march, he would not allow it to be used in advanced positions, and the Paraguayans took to making grass fires to obscure the area with smoke.^{[107][109][110]} Altogether some 20 ascents were made.^[111]

As a general López has been criticised for frequently sending units on attacking manoeuvres which, although audacious, had no clearly defined military objective, thus frittering away his scarce manpower.^[112][113] Even so, by continually taking the initiative the Paraguayans helped to depress the allied soldiers, bored by their own side's caution.

"When López wanted news from the allied camp, he used to send some of his spies to kidnap a sentry, in which they were very successful", said Thompson. Sometimes a sentry would be snatched away^[114] or be stabbed to death silently in the dark.^[115] As noted, allied convoys were frequently attacked, and cavalry patrols led into ambushes.^[82][116]

The Paraguayan soldier's indifference to danger was legendary. In his memoirs George Thompson, who rose to be a lieutenant colonel in the Paraguayan army, wrote "If a Paraguayan, in the midst of his comrades, was blown to pieces by a shell, they would yell with delight, thinking it a capital joke, in which they would have been joined by the victim himself had he been capable".^[117]

Paraguayan soldiers were strictly disciplined. Even a corporal could give any soldier three blows with his cane on his own authority; a sergeant, twelve; an officer, almost any number.^[118] Thompson recalled:

The Paraguayans were the most respectful and obedient men imaginable... A Paraguayan never complained of an injustice, and was perfectly contented with whatever his superior determined. If he was flogged, he consoled himself by saying, 'If my father did not flog me, who would?' Everyone called his superior officer 'his father', and his subordinate 'his son'. López was called 'taitá guasú',^[k] or big father.

As in the French army, all officers were promoted from the ranks. "Young men of good family, who were enlisted, had to take off their shoes and go barefooted, as none of the Paraguayan soldiers were allowed to wear shoes".^[119]

Such was Humaitá's reputation for impregnability that it was referred to in the American or European press as the Gibraltar, Sebastopol or Vicksburg of South America.^[l] This led observers to expect a formidable structure of brick or masonry and they were disappointed when they saw the reality. However, the fortress' real strength lay in its natural defences.^[120]

Its strategic purpose was to stop enemy ships invading Paraguay. The site was a tight, 2,500 yard, horseshoe bend in the river surmounted by a low cliff; a sequence of batteries overlooked the bend and could concentrate converging fire upon the shipping. To prevent enemy vessels dashing past the batteries at full speed there was a chain boom that could be raised to detain them under the guns.^[121]

Around this time ironclads (vessels protected by thick iron plates) were being adopted in warfare, and Brazil had a number of these. Immensely strong, none were sunk by Paraguayan gunfire (although one was lost to a "torpedo", see below). However their disadvantage was that they were so heavy that they might run aground when the river Paraguay fell (which happened seasonally, by as much as 14 feet)^[91] leaving them trapped.^[122]

Further to deter enemy ships there were "torpedoes" — really, improvised naval mines — that could be tethered or released in the stream. These were very unreliable, and usually failed to go off on target, but as Burton remarked "even disciplined men feel a natural horror of, and are easily demoralized by, hidden mysterious dangers so swiftly and completely destructive".^[123] Indeed, the Paraguayans did manage to sink one Brazilian ironclad, Rio de Janeiro, using these mines.^[124]

They made the Brazilian naval command very reluctant to proceed.^[125] They had to be cajoled and persuaded by the Brazilian government.

The fortress proper was protected on the landward size by natural defences (see above, Terrain), and by 8 miles (13 km) of earthworks.^[126] The whole installation was defended by 400 artillery pieces.^[127] (The illustration shows one of the most famous, the Cristiano, which survives today.)^[128] A system of telegraph lines could send troops swiftly to any threatened point.

At this time the whole installation was garrisoned by a force of 20,000 troops, of which at least 10,000 were first class fighting men; Paraguayan soldiers were famed for their valour and ferocity.

After Humaitá was taken, some detractors said its strength had been grossly exa