Throughout history, many people have debated the ethics of war and peace, leading to the creation of just war theory. There have been a number of wars in the past and even in the world today that have been proven unjustified by means of this theory. In my opinion, any war is difficult to justify due to the violence, destructiveness, nature of humans during war and the impact it has on humans and the world. However, I chose to discuss why the American decision to enter World War II was justified and prove it using just war theory, focusing primarily on jus ad bellum. Understand and explain America's decision to enter World War II. II in 1941 is to take a few steps back to when war broke out and why. War broke out in 1939 when Nazi Germany invaded and successfully captured Poland. It was only two days later that Britain and France declared war on Germany, starting World War II. But before explaining this further, it is important to know what were the main causes that led to World War II. Now let's go back to the year 1919, when the First World War ended. World War I officially ended on June 28, 1919 with the signing of the Treaty of Versailles. The details of the Treaty of Versailles were negotiated and finalized in Paris, France, at the Paris Peace Conference. The debate on the treaty opened on January 18, 1919 and was largely controlled by the number of Allied powers participating while Germany was not even invited. However, it was the “big three” who had the most influence at the conference during the development of the treaty. The group that was nicknamed the "Big Three" consisted of Prime Minister David Lloyd of the United Kingdom...... middle of paper ... they and America began to become more involved in the war. On September 27, 1940, the leaders of Germany, Italy, and Japan met in Berlin to sign the Tripartite Pact. The Tripartite Pact formed an alliance against the Allied Powers that established Axis power. It was also a warning to the United States to stop aiding England and France. The United States then initiated "Lend-Lease" which allowed President Roosevelt to send annulation equipment and other war supplies to England and France. As of this discussion, the United States was no longer a neutral nation. Works Cited “The Avalon Project: The Treaty of Versailles of June 28, 1919”. The Avalon Project: The Treaty of Versailles of June 28, 1919. Np, nd Web. March 31, 2014 Crossland, David. “Germany Set to Make Final Payment of World War I Reparations.” ABC News. ABC News Network, September 29, 2010. Web. March 31. 2014