The significance of the establishment of NATO (North Atlantic Treaty Organization) in 1949 was its role in ensuring collective defense among member states during the Cold War. Formed in response to perceived threats from the Soviet Union, NATO aimed to provide mutual protection against aggression. This alliance solidified military and political ties between Western nations, enhancing their security. It also served as a counterbalance to the Warsaw Pact. NATO's establishment marked a crucial step in shaping post-war European security architecture and contributed to the stability of member nations against external threats.