American citizens died when German submarines sank European ships.
The US revolutionary war
Germany's unrestricted submarine warfare
Un-restricted submarine warfare
unrestricted submarine warfare
Submarine Warfare
submarine
Germany's return to unrestricted submarine warfare.
1. Unrestricted Submarine Warfare 2. Sinking of several US ships
A submarine sunk the liner 'Lusitania'. Many Americans died. USA was horrified, declared war on Germany.
The announced resumption of un-restricted submarine warfare.
announced its policy of unrestricted submarine warfare
unrestricted submarine warfare