The Soviet Union tested its first atomic weapon in 1949, but Stalin seems to have viewed possessing it as a political rather than military benefit, and he did not integrate atomic weapons into the Soviet military's equipment. A 1951 Warsaw Pact war plan for Poland was, Vojtech Mastny wrote, "unequivocally defensive" even while "NATO was haunted by the nightmare of armed communist hordes sweeping all but unopposed through Europe". The Soviets assumed that Western forces were ready to invade and that Eastern Europeans would see them as liberators; as in the West, the Soviets overestimated their enemies' strength.