NATO's operations, particularly the international peacekeeping mission in Afghanistan, will be the major topic at the Bucharest summit from Wednesday to Friday.
NATO considers the success of its expeditionary operations essential to its transformation. The following is a brief introduction to the alliance's major operations across the world.
NATO took over control of the International Security Assistance Force (ISAF) in 2003. After four stages of expansion, ISAF, which was initially deployed in the Afghan capital of Kabul only, now covers the whole country.
ISAF is now 47,000 troops strong with the participation of all 26 NATO allies. Thirteen non-NATO countries are also contributing troops to the mission.
In the past few months, NATO allies have been wrangling over burden sharing in Afghanistan. Only four NATO allies -- Britain, Canada, the Netherlands and the United States -- are engaged in fighting the Taliban and al-Qaida terrorists in the south and east of the country.
Despite repeated calls from Washington, major European allies refused to commit more troops or to allow their troops already in Afghanistan to fight in the south of the country.
Canada has threatened to withdraw its troops by 2009 unless a European ally comes to its help. The internal strife was alleviated by French President Nicolas Sarkozy's announcement last Wednesday that his country will send more troops to Afghanistan. NATO leaders are also expected to adopt a "vision statement" that aims to set up a strategy for the years to come. The leaders want the Afghanistan government and other international players to do more in that country.
NATO sent a peacekeeping mission to the Serbian province of Kosovo after its 78-day air strikes against the former Federal Republic of Yugoslavia in 1999.
After Kosovo's unilateral declaration of independence in February, NATO's Kosovo Force (KFOR), stepped up its operations in order to prevent violence, particularly in the Serb-dominated communities.
NATO insists that the 16,000-strong KFOR will remain in Kosovo, arguing that UN Security Council Resolution 1244, which established the force, still serves as the legal basis for its presence in the region.
NATO is helping Iraq by training Iraqi security personnel and supporting the development of the country's security institutions.
NATO has a training center for middle and senior level officers in the outskirts of Baghdad and a language school in the capital city. The alliance is also training Iraqi personnel outside Iraq.
NATO personnel are not involved in any combat activities in the country.
Under "Operation Active Endeavor," NATO naval forces are patrolling the Mediterranean to monitor shipping and provide escorts to non-military vessels through the Straits of Gibraltar.
The operation, launched in the aftermath of the Sept. 11 terror attacks in the United States, is aimed primarily at protecting Europe's key energy supply routes, though it was nominally aimed at halting terrorism-related activities in the Mediterranean. Non-NATO countries like Russia and Ukraine have also contributed ships to the operation.