Three key events that helped shape modern U.S. foreign policy were the Spanish American War, World War I, and World War II. The Spanish American War was between Spain and America in 1898. Cubans were revolting against their Spanish rule, and Americans heard reports of Spanish "atrocities" which were blown out of proportion by the newspapers. The American battleship "Maine" mysteriously sunk in Havana's harbor, and President William McKinley reluctantly declared war. America won the war in ten weeks, and they gained control of Cuba and indefinite colonial power over Puerto Rico, Guam, and the Philippines. This was the first time America had entered into colonialism, and they still have power over Guam and Puerto Rico today. It gave the country new respect in the world, and it created the need to create guidelines for governing and watching out for these colonies. This also shapes our policy today because we still have influence over these areas, and that indicates our power to other nations of the world.

World War I changed Europe forever, and the United States, too. Woodrow Wilson tried to stay out of the war, but public opinion, and growing German influence around the world made Wilson declare war in 1917. After the war ended, President Wilson worked to promote the League of Nations, which was formed in 1919. The League of Nations would eventually evolve into the United Nations, and it hoped to prevent war through negotiation and arbitration. They created many treaties that dealt with social consequences and protection of people, and it helped show how influential the United States was in world affairs after the war. It helped increase our power and prestige, because we helped create the League, and it showed that the U.S. was interested in fostering a better world, especially in war-torn Europe. It shaped our future policy by establishing that we were interested in helping the world, and that we cared about peace and social consequences.

World War II established that the United States was a formidable opponent, and that we could dominate the world if we chose. It also showed the world again that we were compassionate and wanted peace, when we helped rebuild Europe and even flew in supplies during the Berlin Airlift. Our foreign policy toughened after this war, when the Soviet Union challenged us and our nuclear abilities, and it became clear to the world that we would not step down, we would hold our ground and defend ourselves, even as we grew far more influential and involved in foreign policy around the world.