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.