U.S. officials said Monday they will press forward with the war in Iraq a day after the overall U.S. death toll in the five-year conflict rose to 4,000.

The White House called the grim milestone "a sober moment." Here is a look at some other major conflicts in U.S. history, their duration and the number of Americans killed in each.

The Vietnam War: 58,000 American troops killed

The war between the communist Democratic Republic of Vietnam and the U.S. hyphen supported Republic of Vietnam began in 1959, although the U.S. didn't officially enter the war until 1965, when it sent troops to South Vietnam to help prop up the collapsing anti-communist government. By 1975, all of Vietnam was under communist control. About 3 million to 4 million Vietnamese and 1.5 million to 2 million Lao and Cambodians died in the war.

The Korean Conflict: 36,570 American troops killed

On June 25, 1950, North Korea invaded South Korea. Two days later, the 7th Fleet was deployed to the region to prevent the spread of the conflict. The first U.S. infantry units arrived to bolster South Korea's defenses on July 1. The U.S., North Korea and China signed an armistice treaty on July 27, 1953. Total deaths are unknown because of conflicting data, but estimates run into the millions.

World War II: 407,318 American troops killed

In mid-1937, Japan invaded China. In March 1938, Germany annexed Austria, and in March 1939 it occupied Czechoslovakia. In 1941 Japan attacked Pearl Harbor and the U.S. entered the war. In 1944 the Western Allies invaded France. Germany surrendered on May 8, 1945. Japan surrendered on Aug. 15, 1945. About 20 million soldiers and 40 million civilians died in the war.

World War I: 116,708 American troops killed

Archduke Franz Ferdinand, heir to the Austro-Hungarian throne, was killed on June 28, 1914. The Austria-Hungary retaliation set off a chain reaction of war declarations. The British learn ed that Germany want ed Mexico to join the war in 1917. Woodrow Wilson called for war on Germany, which the U.S. Congress declared on 6 April that year. By the end of the war in 1918, more than 20 million people, including 10 million military personnel, were dead.

The U.S. Civil War: 360,222 Union and 258,000 Confederate troops killed

On Nov. 6, 1860, Abraham Lincoln was elected president. On Dec 20, South Carolina became the first state to secede from the Union. The Confederate States of America formed Feb. 9, 1861, and the Confederates attacked Fort Sumter on April 4 that year. On July 4, Congress authorized the call-up of troops to defend the Union. The war turned against the South when the North won the Battle of Gettysburg on July 3, 1863. The Confederates surrendered at Appomattox, Va., on April 9, 1865.