Underseaboats.
Submarine warfare is a military tactic used by many nations where submarines are used to attack enemy ships or as a direct deterrent. This was used extensively by the Germans during World War II.
During WW2, all the major countries involved used submarines.
Submarine warfare was abhorrent in the US during WW1. The British sank US ships trying to enter blockaded German ports. The same is true of US ships trying to enter blockaded British ports. However the Germans use submarine warfare to sink a USS Lusitania. That was the tipping for the US. Prior to then we were not wanting to get into "entangling alliances.
In almost all navies during WWII, submarines were called "boats"...not ships. In Germany, a sub was called an "under-sea-boat", with German enthusiasts preferring to use the German spelling/pronunciation of "boot" for boat. Bottom line: "U-Boat submarine warfare..." is simply submarine warfare (Sub Warfare is what most boys in America grew up calling it).
The Uboat was a submarine made by the Germans
During the Treaty of Versailles
The Chester is a historical submarine that served in the United States Navy during World War I. Originally designated as a cargo ship, it was converted into a submarine chaser. The vessel played a role in anti-submarine warfare efforts in the North Atlantic. Its legacy reflects the naval innovations and strategies employed during that era.
Two actions that upset the Americans during World War I were Germany's unrestricted submarine warfare and the interception of the Zimmermann Telegram. The unrestricted submarine warfare led to the sinking of civilian and commercial ships, including the Lusitania, which resulted in American casualties. Meanwhile, the Zimmermann Telegram revealed Germany's proposal to Mexico to join the war against the U.S., further inflaming American public sentiment and prompting the U.S. to enter the conflict.
Most likely Germany, they had the U-boats (underwater boats)
What political group wanted to take power in Germany during WW1.
Gas was first used in warfare during the Second Battle of Ypres in 1915 by the Germans.