World War II: Tehran Conference: U.S. President Franklin D. Roosevelt, British Prime Minister Winston Churchill and Soviet Premier Joseph Stalin meet in Tehran, Iran, to discuss war strategy.

World War II or the Second World War was a global conflict between two coalitions: the Allies and the Axis powers. Nearly all of the world's countries participated, with many nations mobilising all resources in pursuit of total war. Tanks and aircraft played major roles, enabling the strategic bombing of cities and delivery of the first and only nuclear weapons ever used in war. World War II is the deadliest conflict in history, causing the death of 70 to 85 million people, more than half of whom were civilians. Millions died in genocides, including the Holocaust, and by massacres, starvation, and disease. After the Allied victory, Germany, Austria, Japan, and Korea were occupied, and German and Japanese leaders were tried for war crimes.

The Tehran Conference was a strategy meeting of the Allies of World War II, held between Joseph Stalin, Franklin D. Roosevelt, and Winston Churchill from 28 November to 1 December 1943. It was the first of the Allied World War II conferences involving the "Big Three" and took place at the Soviet embassy in Tehran just over a year after the Anglo-Soviet invasion of Iran. The meeting occurred shortly after the Cairo Conference was held in Egypt for a discussion between the United States, the United Kingdom, and China from 22 to 26 November 1943. The Big Three would not meet again until 1945, when the Yalta Conference was held in Crimea from 4 to 11 February and the Potsdam Conference was held in Allied-occupied Germany from 17 July to August 2. Notably, President Franklin D. Roosevelt arrived on the USS Iowa.

The president of the United States (POTUS) is the head of state and head of government of the United States. The president directs the executive branch of the federal government and is the commander-in-chief of the United States Armed Forces.