Final answer:
The RMS Lusitania, a British steamship, was torpedoed by a German U-boat on May 7, 1915, leading to the loss of over 1,200 lives, including 128 American citizens. This event significantly influenced WWI-era sentiments and highlighted the destructive power of submarine warfare.
Step-by-step explanation:
The British steamship that the Germans torpedoed, resulting in the death of 100 US citizens, was the RMS Lusitania. On May 7, 1915, this British ocean liner was traveling from New York to Liverpool when it was attacked by a German U-boat off the coast of Ireland. The Lusitania sank in about 18 minutes, and of the more than 1,200 passengers who perished, 128 were American citizens. The event caused an outcry in the United States and was a key factor in turning public opinion against Germany during World War I.
The sinking of the Lusitania by German submarines demonstrated the brutal capabilities of naval warfare during that time. Although it was carrying a significant amount of ammunition, which the Germans cited as a reason for declaring it a legitimate target, the loss of civilian lives had a dramatic impact on international reaction to the incident. The tragedy represented one of the earliest instances of submarine warfare gaining global attention and remains an infamous example of the casualties of wartime naval strategies.