The United Nations
The United Nations is an international organization founded at 1945 at the end of World War II.. It was the successor to the failed League of Nations that had been formed after the First World War. However, the United Nations had the full support and funding of the United States (the headquarters of the UN is centered in New York City) and more significantly was endowed with a military force to provide its directives with some backing. The League of Nations had lacked an such military powers and that was regarded as the chief reasoning behind its failure.

The United Nations is headed by the five permanent members of the Security Council, the United States, Russia, Great Britain, France and China (reflective of the allies of WWII). Other members of the council are elected and serve on a rotating basis. The most significant power of the security council is the ability to veto UN initiatives that have been approved by the General Assembly, of which all member nations are voting members.

UN initiatives such as the "police action" of the Korean War and securing of East Timor in Indonesia highlight the ability of the UN to mobilize military personnel in defending nations from aggression. Other UN initiatives include the World Health Organization, focused on the distribution of food and medicines. Also of significance is the International Court of Justice located at The Hague, a world forum for the prosecution and trial of war crimes charges against aggressive national leaders committing "crimes against humanity".

North Atlantic Treaty Organization (NATO)
NATO was formed in 1948 as a "collective security" force to resist the further spread of communism in Europe. Following the Second World War the USSR did not withdraw from the nations of Eastern Europe that it had liberated from Nazi control, instead forcing in communist regimes under Soviet domination. As the "iron curtain" fell, the democratic nations of Western Europe, the United States and Canada designed NATO as a resistance to further spread. The communist bloc nations, under Soviet control, formed the Warsaw Pact as a communist collective security arrangement to counter the NATO agreement.

NATO was founded under the concept of collective security or "collective self-defense" as it is termed in the NATO charter. This concept calls for any attack on a NATO member nation to be perceived as an attack upon all NATO member nations. This idea of collective security is fundamental to NATO's success, the threat of a collective response kept the spread of communism in Europe in check and helped maintain peace and stability in Europe for the past 50+ years.

In recent years NATO has expanded its membership, in the wake of communism's fall the nations of the former Warsaw Pact such as Poland and Czechoslovakia have been welcomed into the organization. The NATO alliance has not only served as collective defense, but furthered economic ties and cooperation between the member states. Also in recent years NATO has taken a more active role in preventing European aggression before it sparks wider conflict. The 1999 NATO bombing campaign in Serbia and Kosovo as well as the stationing of NATO troops in the former Yugoslavia to maintain peace serve as the best example of NATO's this evolving role in the post-Cold War world.

Southeast Asian Treaty Organization (SEATO)
Active from 1954-1977 SEATO was designed similarly to the North Atlantic Treaty Organization (NATO), and intended to prevent the spread of communism. However, unlike NATO, SEATO did not contain the collective security provisions that called for an attack upon one member as being an attack upon all member nations. Following the US involvement in the Vietnam war, the organization was disbanded as the willingness of member nations to defend against communism declined.

Organization of American States (OAS)
Founded in 1948 as another international organization intended to repeal the further spread of communism, the OAS covers the 35 nations of the Western Hemisphere.  The treaty requires member nations to assist other member nations in resisting armed attack as well as negotiating conflicts between members in an effort to achieve a peaceful resolve to disputes. The OAS also works to promotes the development of democratic governments and protect human rights in the regions in addition to encouraging economic development, social and cultural exchange between members.