Operation Inherent Resolve
 Operation Inherent Resolve (OIR) is the United States military's operational name for the international war against the Islamic State (IS)[101]—a group also known as the Islamic State of Iraq and Syria (ISIS), the Islamic State of Iraq and the Levant (ISIL) or its Arab acronym "Daesh"—including both a campaign in Iraq and a campaign in Syria, with a closely related campaign in Libya. Through 18 September 2018, the U.S. Army's III Armored Corps was responsible for Combined Joint Task Force – Operation Inherent Resolve (CJTF—OIR) and were replaced by the XVIII Airborne Corps.[102] The campaign is primarily waged by American and British forces in support of local allies, most prominently the Iraqi Security Forces (ISF) and Syrian Democratic Forces (SDF). Combat ground troops, mostly special forces, infantry, and artillery have also been deployed, especially in Iraq. Of the airstrikes, 70% have been conducted by the military of the United States, 20% by the United Kingdom, and the remaining 10% being carried out by Australia, Belgium, Canada, Denmark, France, Jordan, the Netherlands, Saudi Arabia, Turkey, and the United Arab Emirates.[103] According to the Pentagon, by March 2019, the day of IS's territorial defeat in Syria, CJTF—OIR and its partner forces had liberated nearly 110,000 square kilometers (42,471 square miles) of land and 7.7 million people from IS, the vast majority of the self-proclaimed caliphate's territory and subjects.[104] By October 2017, around the time of IS's territorial defeat in Iraq, CJTF—OIR claimed that around 80,000 IS militants had been killed by it and its allies (excluding those targeted by Russian and Syrian air strikes). By the end of August 2019, it had conducted 34,573 strikes.[86][105][106] Tens of thousands more were killed by partner forces on the ground (the SDF alone claimed to have killed 25,336 IS fighters by the end of 2017).[107] BackgroundThe United States relied on a combination of legal frameworks to justify its use of force against ISIS in Iraq and Syria, namely: military assistance on request, self-defence under Article 51 of the United Nations (UN) Charter, and the "unwilling or unable" doctrine.[108] However, this legal reasoning was not unanimously accepted by other coalition members, resulting in differing geographic scopes of operation—some states restricted their involvement to Iraq, while others also conducted operations in Syria.[109][110] Moreover, these justifications continue to be the subject of legal debate among scholars.[110][111][112][113] Legal basis under international lawInternational law prohibits the use of force against another state, as provided in Article 2(4) of the UN Charter.[114] However, there are two exceptions to 'violate' this legal prohibition, which is through authorisation of the United Nations Security Council (UNSC), as stated in Article 42 of the UN Charter, and in self-defence, in accordance with Article 51 of the UN Charter.[115] Military assistance on requestMilitary assistance provided at the request of a state does not require UN authorisation nor the invocation of Article 51, as it falls within a state’s sovereign right under customary international law to request such assistance and does not necessarily entail the use of force.[116] As such, it does not constitute a 'violation' of the prohibition on the use of force. However, in order to remain within the legal framework of military assistance—rather than constituting an intervention that breaches the prohibition on the use of force—the inviting state determines the scale and scope of the intervening force, as the operation's sole purpose is to provide assistance to the inviting sovereignty.[117] Furthermore, the inviting state cannot legally authorise the use of force on foreign territory, as this would violate Article 2(4) of the UN Charter, therefore, military assistance on request is confined to the borders of the inviting state.[118] In 2014, the Iraqi government submitted two formal letters to the UNSC, requesting military assistance in response to the ongoing threat posed by ISIS along its borders.[119][120] Several states participating in OIR acted solely on the basis of this request, thereby limiting their operations to Iraqi territory, as the Iraqi government had no legal authority to authorise military action on Syrian soil.[121] By responding exclusively to Iraq’s request, the scale and scope of the foreign military presence was determined through agreements with the Iraqi authorities and remained confined within Iraq’s borders, despite ISIS maintaining a stronghold in eastern Syria.[122] The Obama administration relied on this legal framework—military assistance upon request—to justify its operations within Iraq.[108] However, as Syrian President Bashar al-Assad had not granted consent for foreign military intervention, an alternative legal basis was required to justify military action against ISIS in Syria.[123][124] Additionally, scholars such as Ashley Deeks have argued that the U.S. tends to avoid relying on military assistance upon request as a legal framework, as such operations are entirely dependent on the level of consent granted by the inviting state and could require the U.S. to withdraw its forces should that state revoke its request.[118] Article 51: Individual or Collective Self-defenceTo justify its operations within Syria, the United States invoked Article 51 of the UN Charter, citing the principle of collective self-defence on behalf of Iraq.[108] This was based on the Iraqi government’s request for a U.S.-led international campaign against ISIS.[120] Simultaneously, the United States also invoked the right of individual self-defence, referencing the threat posed by ISIS to its own national security.[108] Article 51 of the UN Charter provides the "inherent right of individual or collective self-defence if an armed attack occurs against a Member of the United Nations".[125] In 1986, during the N | ||||||||||||||||||||||||||||||||||||
