Second, watch for military participants to scale back their commitments or leave the coalition altogether. In April 1991, a U.S.-Britain-France coalition formed to enforce a no-fly zone over the territory of Iraq north of the 36th parallel; one year later, it established another no-fly zone south of Iraq’s 32nd parallel. However, in practice, only U.S. aircraft attacked Iraq’s air-defense radars and surface-to-air missiles when the coalition was threatened. Moreover, in 1996, when Washington and London announced that the southern no-fly zone would expand to the 33rd parallel, France refused to patrol within this area. Soon after, France quit both no-fly zones altogether, on the grounds that what had begun as a primarily humanitarian mission had become a tool to punish Saddam Hussein.

Similarly, the March 2011 air war over Libya began with eight countries participating in airstrikes against the security forces of Muammar al-Qaddafi. But five of the countries had to reduce the tempo of their airstrikes at various times when they ran out of munitions. Denmark was limited in what it could bomb, as it lacked targeting intelligence. France and Italy withdrew their aircraft carriers after five months, and Norway stopped participating after six months because, as its defense minister, Grete Faremo, announced, its forces could not “maintain a large fighter jet contribution during a long time.” On March 28, 2011, Obama declared, “The United States will play a supporting role — including intelligence, logistical support, search and rescue assistance, and capabilities to jam regime communications.” Unsurprisingly, given its vastly superior military and intelligence capabilities, the United States would eventually play both the supporting and lead roles — and we should expect this with regards to the Islamic State campaign as well.