During the early years of World War I, which of the following did the Germans use to great advantage? the field telephone the machine gun the submarine the tank

Submarine--Germany used a policy of unrestricted submarine warfare.

Germany used submarines or U-boats to attack shipping vessels on the Atlantic as well as British war ships. The goal of the submarine warfare was to shut down the British navy and to prevent goods from reaching England from the US. Unrestricted submarine warfare was a policy used by Germany in which they would attack any and all ships within their path. This policy resulted in controversy when passenger boats were attacked such as the Lusitania. The attack on the Lusitania began to turn US opinion against Germany and forced the US to make a statement against the German policy.

During the early years of World War I, the Germans used "the submarine" to a great advantage, since they practiced "unrestricted submarine warfare," which led to the destruction of a lot of enemy property.