<P> The US, the UK, and most other NATO countries opposed efforts to require the U.N. Security Council to approve NATO military strikes, such as the action against Serbia in 1999, while France and some others claimed that the alliance needed UN approval . The US / UK side claimed that this would undermine the authority of the alliance, and they noted that Russia and China would have exercised their Security Council vetoes to block the strike on Yugoslavia, and could do the same in future conflicts where NATO intervention was required, thus nullifying the entire potency and purpose of the organization . Recognizing the post-Cold War military environment, NATO adopted the Alliance Strategic Concept during its Washington summit in April 1999 that emphasized conflict prevention and crisis management . </P> <P> The September 11 attacks in the United States caused NATO to invoke Article 5 of the NATO Charter for the first time in the organization's history . The Article says that an attack on any member shall be considered to be an attack on all . The invocation was confirmed on 4 October 2001 when NATO determined that the attacks were indeed eligible under the terms of the North Atlantic Treaty . The eight official actions taken by NATO in response to the attacks included Operation Eagle Assist and Operation Active Endeavour, a naval operation in the Mediterranean Sea which is designed to prevent the movement of terrorists or weapons of mass destruction, as well as enhancing the security of shipping in general which began on 4 October 2001 . </P> <P> The alliance showed unity: On 16 April 2003, NATO agreed to take command of the International Security Assistance Force (ISAF), which includes troops from 42 countries . The decision came at the request of Germany and the Netherlands, the two nations leading ISAF at the time of the agreement, and all nineteen NATO ambassadors approved it unanimously . The handover of control to NATO took place on 11 August, and marked the first time in NATO's history that it took charge of a mission outside the north Atlantic area . </P> <P> ISAF was initially charged with securing Kabul and surrounding areas from the Taliban, al Qaeda and factional warlords, so as to allow for the establishment of the Afghan Transitional Administration headed by Hamid Karzai . In October 2003, the UN Security Council authorized the expansion of the ISAF mission throughout Afghanistan, and ISAF subsequently expanded the mission in four main stages over the whole of the country . </P>

Why did the us canada and most western european countries form the nato