Founded in 1949, with the Washington Treaty, as a protecting organization of peace in Cold War. NATO was really the only powerful structure at that times with its military. Every member country in NATO contributed in material and/or staff terms in NATO, which mostly done by the USA, and it aimed to sustain peace against its rival Soviet Union and its alliances "Warsaw Pact".
The fall of Berlin Wall in 1989 not only changed many things globally but also the strcuture and organization of NATO. Starting from 1991, NATO contacted to the former members of the Warsaw Pact and the countries like Hungary, Romania, Bulgaria, Poland begun to be the members of NATO.
Following the changes in the world and desolution of the Soviet Union, NATO continued its peackeeping mission in Afghanistan. ISAF (International Security Assistance Force) with its headquarter in Kabul started to keep Afghanistan safe. ISAF also contirbuted many construction and maintenance works throughout the country. It had been contributed by many countries in the world, not only the NATO members like the USA, the UK, Turkey, Germany but also South Korea, Malaysia, Macedonia, Azerbaijan. Together with the UN and EU, NATO, according to me is the most successful intenational organization which has an active agenda with many work that had to be completed and good historical background.
As can be seen despite the politacal change in global terms NATO still is active and seems it will be the most active one in the following years among the other international groups and organizations.