The United States of America joined in the World War II after 7th of December, 1941; the day on which it's Pearl Harbor was attacked. Prior to this America had stayed away from the war and wasn't a part of either the Allied or the Axis powers. However, when Japan destroyed almost the entire American navy with a surprise bombing of Pearl Harbor which was of its primary naval bases, the U.S joined in fighting along side France and Britain.
The longest war the United States ever entered was the Vietnam War.
The US entered World War 1 on April 6, 1917. The war ended about one and a half years later.
The US entered when it declared war on Germany on April 6th 1917. So they entered late.
The US entered WW1 in 1917. The US entered WW2 in 1941.
The United States entered World War II after the Japanese attack on Pearl Harbour on 7th December 1941. The US declared war on the following day, 8th December 1941.
1917 smart
1941
1917.
Un-restricted submarine warfare. If it wasn't for that, the US would not have entered the war. As it was, the US was only in it for a year anyway...it ended in 1918 (the US entered the war in 1917).
As soon as the US entered the war in December 1941
April 1917
1909 to 1944 The US entered World War 2 in December of 1941.
The US entered the war on April 6,1917
The US entered World War 1 on April 6, 1917. It remained in the war until it ended about a year and a half later.
The allies entered the war in 1914; the US entered the war in 1917.
the Atlantic Ocean.
The longest war the United States ever entered was the Vietnam War.