the Lusitania was a british passenger liner that had Americans on board when she was sunk, not sure of another one. the zimmerman note was also a major cause. In it, the Germans attempted to convince Mexico to attack the united states from the south in order to create another front. the US was still neutral at the time the note was sent but they did not stay that way for long.
after 1) Germany's submarines sunk their ships 2) they intercepted the zimmerman telegraph
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The Zimmerman Telegram and hundred of American ships being sunk by German submarines led to the U.S declaration of war on Germany.
Counting warships & merchantman, US subs sunk about 1,000 vessels.
4,837
There were no submarines sunk or damaged during the attack on Pearl Harbor; all vessels either sunk or damaged were capital ships (battleships, cruisers, etc.) or support vessels (tenders, tugs, etc.).
Germany sunk the ships themselves. They did the WHOLE thing.
109 ships of 593,864 tons in Atlantic
The Sussex Pledge was made by Germany after the US threatened to cancel diplomatic relations with Germany after Germany sunk a French channel ferry, Sussex, during WWI. The pledge stated that German submarines would not target passenger ships or merchant ships unless the presence of weapons had been established.
Submarines do get sunk in the sea.
The Lusitania.
This question appears to be about U-Boats or submarines. In WW 1, the Germans had a large submarine fleet that terrorized Atlantic Ocean shipping. For a time, Germany announced that all ships were potential targets. This is one of the several reasons the United States entered WW 1. There were Allied defenses against U-Boats and using various explosives a good number of Germany's submarines were sunk.