Since its origins, in the context of the Cold War's beginning, NATO has been a robust defensive alliance, acting in accordance with UN Charter, as a collective defence structure based on solidarity and mutual trust. Nowadays it has 28 member states and one can say that it fulfilled its main role: to protect the West against communist/Soviet threats using the deterrence and containmemt tools. Neither USSR nor its main instrument, the Warsaw Pact dare to attack the Euro-Altantic area. Our main assumption is that because the specific national interests of each member state, because of the domestic-constitutional issues and bureaucratic obstacles, the Alliance cannot yet forge a common strategic culture for all its members and also lacks a common lens for detecting real risks and therats, be they nation states or non-states actors. Nowadays, Russia and Islamic State are the main adversaries for the Western states, thus NATO should be more effective in dealing with them. And there is a need for reform and transformation. Divergences between adepts of territorial defence and those of pro-active "out of area" missions go in addition to divergences concerning the neeed for increased defence budgets for all members and especially concering the attitude towards Russia. Moscow used economic and energy tools trying to divise some allies like Hungary, Greece and Bulgaria and it partially succeeded. Using some theories of alliances and of democratic peace, resorting to recent facts and figures related to NATO's activities and plans, will help the reader understand the problem of increasing the power vs. increasing the security dilemma and the prospect of future conflicts.