<P> The intervention in Afghanistan (Operation Enduring Freedom--Afghanistan) to depose that country's Taliban government and destroy training camps associated with al - Qaeda is understood to have been the opening, and in many ways defining, campaign of the broader War on Terrorism . The emphasis on Special Operations Forces (SOF), political negotiation with autonomous military units, and the use of proxy militaries marked a significant change from prior U.S. military approaches . </P> <P> In January 2002, the U.S. sent more than 1,200 troops (later raised to 2,000) to assist the Armed Forces of the Philippines in combating terrorist groups linked to al - Qaida, such as Abu Sayyaf, under Operation Enduring Freedom--Philippines . Operations have taken place mostly in the Sulu Archipelago, where terrorists and other groups are active . The majority of troops provide logistics . However, there are special forces troops that are training and assisting in combat operations against the terrorist groups . </P> <P> After the lengthy Iraq disarmament crisis culminated with an American demand that Iraqi President Saddam Hussein leave Iraq, which was refused, a coalition led by the United States and the United Kingdom fought the Iraqi army in the 2003 invasion of Iraq . Approximately 250,000 United States troops, with support from 45,000 British, 2,000 Australian and 200 Polish combat forces, entered Iraq primarily through their staging area in Kuwait . (Turkey had refused to permit its territory to be used for an invasion from the north .) Coalition forces also supported Iraqi Kurdish militia, estimated to number upwards of 50,000 . After approximately three weeks of fighting, Hussein and the Ba'ath Party were forcibly removed, followed by 9 years of military presence by the United States and the coalition fighting alongside the newly elected Iraqi government against various insurgent groups . </P> <P> With the emergence of ISIL and its capture of large areas of Iraq and Syria, a number of crises resulted that sparked international attention . ISIL had perpetrated sectarian killings and war crimes in both Iraq and Syria . Gains made in the Iraq War were rolled back as Iraqi army units abandoned their posts . Cities were taken over by the terrorist group which enforced its brand of Sharia law . The kidnapping and decapitation of numerous Western journalists and aid - workers also garnered interest and outrage among Western powers . The US intervened with airstrikes in Iraq over ISIL held territories and assets in August, and in September a coalition of US and Middle Eastern powers initiated a bombing campaign in Syria aimed at degrading and destroying ISIL and Al - Nusra - held territory . By December 2017, ISIL had no remaining territory in Iraq, following the 2017 Western Iraq campaign . Airstrikes by US and Coalition forces have continued in Syria against the Assad government especially after the Douma chemical attack in 2018 . </P>

Which event allowed britain to focus its military resources on fighting the united states