Which 1949 alliance committed Western nations to mutual defense against aggression?

• A. North Atlantic Treaty Organization
• B. Warsaw Pact
• C. United Nations
• D. SEATO

Answer: (A)

Mutual defense and collective security in the early Cold War. NATO was created in 1949 to bind Western nations to defend one another if any member is attacked. The treaty established that an armed attack against one member is considered an attack against all, triggering a coordinated response. This was aimed at deterring Soviet expansion and ensuring security for Western Europe through a permanent alliance that included major powers like the United States and Western European countries. The other choices don’t fit because the Warsaw Pact came later in 1955 as a Soviet-led counterpart, SEATO was formed in the 1950s for Southeast Asia, and the United Nations is a broad international organization rather than a standing mutual-defense treaty.