4. Korean War
In June 1950, the Soviet-supported North Korean military crossed the 38th parallel that divided North and South Korea. Fearful of the spread of communism, President Harry Truman garnered support from allies in the United Nations Security Council to drive the North Korean troops out of the South. General Douglas MacArthur, however, pursued the North Koreans to the Yalu River, which formed the northern border between China and the Korean peninsula. The Chinese interpreted MacArthur’s actions as an act of war and routed the U.N. troops, forcing them to retreat below the 38th parallel. The war eventually ended after Dwight Eisenhower assumed the presidency and threatened the use of nuclear weapons if the North Koreans or Chinese did not respect the 38th parallel as the boundary between the two countries. Ultimately, the Korean War cost the U.S. $341 billion and nearly 34,000 lives.
3. Vietnam War
The war in Vietnam cost the U.S. $738 billion, or just 2.3% of GDP in 1968. By the end of the conflict, the names of more than 58,000 dead soldiers were recorded on the Vietnam Veterans Memorial in Washington, D.C. After North Vietnamese troops drove the French out of the region in 1954, ending a brutal era of colonialism, the Geneva Accords stipulated that elections in the South be scheduled for the following year. Determined not to let communism spread, the U.S. lent its support to Ngo Dinh Diem, a French-educated, Catholic politician in South Vietnam. By the time the U.S. committed troops in 1965, Diem had been assassinated and Vietnamese support for the new military-led South Vietnamese government had faded. With supplies from China and the Soviet Union, North Vietnam primarily used guerilla tactics to attack U.S. troops and bases, often by surprise. By the late 1960s, public support for the war in the U.S. was fading. American troops officially withdrew from the region in 1973 and South Vietnam fell to communism in 1975.
2. War on Terror
Conflicts in Iraq and Afghanistan following September 11, 2001 — collectively known as the War on Terror — cost the U.S. more than $1.6 trillion through 2010. The U.S. entered Afghanistan in October 2001, to search for Osama bin Laden, the mastermind behind the terrorist attacks in New York and Washington D.C., and to overthrow the Taliban government, which was long suspected of harboring terrorists. U.S. troops invaded Iraq and overthrew Saddam Hussein in 2003 operating on the belief that he had weapons of mass destruction. Elections in both Iraq and Afghanistan, as well as training military personnel in each country to help stabilize the region, are both heralded as successes. Despite these successes, both countries continue to be marred by conflict.
1. World War II
Once the U.S. emerged from its isolationist shell, it spent more than $4 trillion fighting in World War II and lost more than 400,000 troops. U.S. involvement officially began on December 8, 1941, the day after the Japanese bombed Pearl Harbor. America officially declared war against Germany and Italy three days later. After conquering a number of European countries, Germany focused its attention on the Soviet Union. By 1944, Soviet forces were successfully driving German troops west. On June 6, 1944, Allied forces landed on the beaches of Normandy, pushing east into Europe, and splitting the Germans along two fronts.
In the Pacific, U.S. military experts estimated that an invasion of Japan would likely result in much greater casualties. President Harry Truman ordered an atomic bomb be dropped on Hiroshima on August 6, 1945. Months earlier, at the Yalta Conference in 1945, Stalin had promised to enter the Pacific front within three months of the war’s end in Europe. If the Soviets were involved in Japan’s defeat, they would likely insist on reparations. To prevent a Soviet claim to Japanese assets, assert U.S.-dominance over Stalin, and secure a Japanese surrender, Truman ordered a second atomic bomb dropped on Nagasaki on August 9, the day after the Soviet Union declared war on Japan. By the end of the war, more than 50 million soldiers and civilians had given their lives, according to conservative estimates.