The North Atlantic Treaty Organization has been in business since 1949. It currently has 28 members and its purpose is to guarantee the safety and security of their freedom in political as well as militarily means if necessary.
For most of its existence NATO has been merely a deterrent to any transgressions that had occurred up to the 1990's. Since the 90's it has been involved in Kuwait and Turkey. It has given aid and assistance to Russia, Kosovo, Afghanistan, African Union and many other duties and missions.
In the beginning it was a deterrent to the Soviet Union and the aggression they showed in Europe after WWII. So as I stated before most of the NATO mission was nothing more than just existing. Now since the world has changed following the breakup of the Soviet Union and with countries making regional warfare it has been more involved.
The question has been asked has NATO outlived its mission and the answer is no. As seen recently with the annexation of the Crimea NATO is an organization that must stay in existence. Europe as individual countries could be run over in days but Europe as a block of nations can withstand anything. The United States is also a member of the organization and relies heavily on friends within the community.
Take for instance with September 11, 2001 when the World Trade Center was attacked, NATO and its members were able to work out just who was involved with the attacks. When the United States went after those involved it was nice to know that we had NATO to cover our backs.
NATO has been in existence for these past 65 years and without it, I would hate to think what kind of world we would be living in.
Russia knows that if it should continue its expansionist mood that NATO would have no problem stepping in and putting an end to it. NATO is an organization that has a vital role in the world just as it did with its conception those 65 years ago. It is here to stay, Comrade.