North Atlantic Treaty was signed on April 4, 1949 by the founder member countries. NATO has its headquarters at Brussels (Belgium).Member countries are situated in North Atlantic region.The total number of the member countries is 19. Alliance was established as a defensive, political and military alliance of independent countries. The member countries promised to maintain and develop their individual and collective capacity to resist armed attack and consult each other if any of the member nations were threatened politically. The armed attack against any of them would be countered by combined action