The RMS Lusitania was sunk on this day in 1915 after being struck by a torpedo fired by a German submarine. The ship was fully underwater in just 18 minutes, and 1,200 people died. It was a turning point in the First World War and one of the reasons the United States would join the Allied powers in the penultimate year of the war.
A few months prior, Germany had warned it would strike anyone conducting shipping activities around Britain. The Lusitania was, technically, registered as a warship as it was meant to be easily converted into one; but on the day it was sunk, the ship was operating as a passenger liner. 128 of those killed were U.S. citizens, causing outrage.
After warnings from the U.S. that Germany needed to cut it out, unrestricted submarine warfare was halted. But Germany resumed the attacks in February 1917; that, plus its attempt to ally with Mexico in case of war with the U.S., basically forced the hand of President Woodrow Wilson to request a declaration of war from Congress. That vote was successfully held in April 1917.
To learn more about the sinking of the Lusitania, check out this article on History.com.
