Excerpts from Books and Wikipedia
"In mid-2014, an international coalition led by the United States intervened against ISIL in Syria and Iraq with a massive airstrike campaign, in addition to supplying advisors, weapons, training, and supplies to ISIL's enemies in the Iraqi Security Forces and Syrian Democratic Forces. This campaign reinvigorated the latter two forces and dealt a huge blow to the nascent Islamist proto-state, killing tens of thousands of ISIL troops and dealing significant damage to their financial and military infrastructure. This was soon followed by a smaller-scale Russian intervention exclusively in Syria, in which ISIL lost thousands more fighters to airstrikes and other Russian military activities and had its financial base even further degraded. In July 2017, the group lost control of its largest city, Mosul, to the Iraqi army, followed by the loss of its de facto political capital of Raqqa to the Syrian Democratic Forces. Following these major defeats, ISIL continued to lose territory to the various states and other military forces allied against it, until it controlled no meaningful territory by November 2017." [Wikipedia]