The U.S entered the war for 2 reasons: 1) A telegraph was sent to the Mexican President from Germany requesting Mexican entry into the war on the side of Germany and the Central Powers and requesting a subsequent Mexican invasion of the United States. The telegraph was intercepted by American intelligence services and this greatly angered Woodrow Wilson and his administration.
2) Germany had un-restricted submarine warfare during World War 1 which means that German submarines indiscriminately shot at civillian vessels from any country (other than their own) without provocation or warning. This method of naval warfare (simplified to commerce raiding) was catostrophic to Germany when a German U-Boat (Submarine) sunk the British HMS Lucitania which held many hundreds of American passengers. The casualties from the sinking od the Lucitania was enormous.
The above reasons are why the United States declared war on Germany in 1917. It should be noted that Germany responded with a large counter offensive on the western front to attack French and British troops before the fresh and battle-ready Americans could join the fight. The offensive was in 1918.
WW I - Lusitania. WW II - Pearl Harbour.
The US entered the war on April 6,1917
The US entered World War 2 after the attack on Pearl Harbor. When over 2,400 US lives were lost in a sneak attack on a Sunday morning, there was no stopping US involvement in the war.
The US finally entered World War I in 1917, when it had bogged down after three years of fighting. The additional manpower turned the tide, and by 1919 Germany had lost most of its territorial gains. The war was ended by the Treaty of Versailles on June 28, 1919.
The allies entered the war in 1914; the US entered the war in 1917.
The sinking of the Lusitania was the reason the US finally entered into World War 1. It was torpedoed by a German U-boat. Almost 2,000 people lost their lives.
The longest war the United States ever entered was the Vietnam War.
The first unemployment crisis from the Depression ended with World War Two. when the US entered the war, millions of peoplpe were employed in factories and assembly lines for the war effort.
1917 smart
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).
The us entered the Vietnamese war in 1950 they exited in 1975 entered to avoid a communist takeover of south Vietnam
please specify which war