Numerous representatives of theories of international relations, security theories or alliance theories have examined the new role of the North Atlantic Alliance or the North Atlantic Treaty Organization (NATO) in the post-bipolar world. Parallel with the theoretical examination of goals and tasks, NATO has transformed itself in practice, following the realities of the contemporary global era. In trying to achieve and keep the primacy of the strongest military- political organization, the Alliance has - especially in the Strategic Concept adopted in Lisbon in 2010-set the normative and institutional foundations of its global engagement, fulfilling the military (hard) and a wide array of non-military (soft) security challenges. This strategy has given rise to "Euro-Atlanticism", as a subsystem of international relations based on strong American-European relations, to fit with the process of regionalization of global politics. However, the 2013-2014 crisis in Ukraine has turned the focus of interest and activities of NATO once again primarily to Europe and it has stressed the importance and necessity of strengthening Euro-Atlantic security and defence ties. The most powerful member of the Alliance, the United States, is again strongly engaged in Europe and Russia, as a kind of successor to the Soviet Union, is once more detected as a major threat to European security. There have been many aspects of theories of international relations that have tried to explain the dynamic of the post-Cold War international community. However, the approach based on neo-realistic assumptions of the role of a security community, collective defence and the use of military force has proved to be dominant. NATO will continue to work on its political dimension as an alliance of the democratic world and the September 2014 Wales Summit will certainly mark the return of NATO to its roots, strengthening its security and military dimensions in the collective defence of Europe from Russia.
After the collapse of the bipolar international order, NATO has been focused on its desire to eradicate Cold War divisions and to build good relations with Russia. However, the security environment, especially in Europe, is still dramatically changing. The NATO Warsaw Summit was focused especially on NATO’s deteriorated relations with Russia that affect Europe’s security. At the same time, it looked at bolstering deterrence and defence due to many concerns coming from eastern European allies about Russia’s new attitude in international relations. The Allies agreed that a dialogue with Russia rebuilding mutual trust needs to start. In the times when Europe faces major crisis from its southern and south-eastern neighbourhood - Western Balkan countries, Syria, Libya and Iraq - and other threats, such as terrorism, coming from the so-called Islamic State, causing migration crises, it is necessary to calm down relations with Russia. The article brings out the main purpose of NATO in a transformed world, with the accent on Europe, that is constantly developing new security conditions while tackling new challenges and threats.