General Washington, for example, instructed his army to intercept letters between British operatives, copy them and allow those communications to go on their way.
President Lincoln used the warrantless wiretapping of telegraph messages during the Civil War to discern the movements and intentions of opposing troops.
President Wilson, in World War I, authorized the military to intercept each and every cable, telephone and telegraph communication going into or out of the United States.
During World War II, President Roosevelt instructed the government to use listening devices to learn the plans of spies in the United States. He also gave the military the authority to review, without warrant, all telecommunications, quote, "passing between the United States and any foreign country."