In the years after World War II, twelve countries in North America and Europe got together to form an alliance. This alliance, known as the North Atlantic Treaty Organization, would build up the collective military and security strength of every country involved - so an attack on one country would mean an attack on them all. How does a security alliance between dozens of countries with different governments, interests, and military power, even work?  What role does NATO play in international war and peace today? Helping us answer those questions are Marla Keenan,  an adjunct senior fellow at the Stimson Center, focusing on international security, including human rights in armed conflict, and the protection of civilians, and Rachel Rizzo,  a senior fellow at the Atlantic Council’s Europe Center whose research focuses on European security, NATO, and the transatlantic relationship.