Dasch enlisted as a private in the US Army and served slightly more than one year, at which time he purchased himself out of the Army and received an honorable discharge.
In 1930, Dasch married Rose Marie Guille, a Native American.
Dasch held various waiter jobs in New York City. Always having dreams of greatness, yet never living up to them. His failures would plague him for the rest of his life.
Dasch and the others were trained for espionage activities against the U.S. in a school specifically used for the training of sabotage agents by the German High Command, on an estate at Quentz Lake, Brandenburg, near Berlin, Germany.
The saboteurs received three weeks of intensive sabotage training and were instructed in the manufacture and use of explosives, incendiary material and various forms of mechanical, chemical, and electrical delayed timing devices. This training was both theoretical and practical. Considerable time was spent by the instructors with the saboteurs in developing complete background histories which they were expected to use in the United States. They were encouraged to converse together in the English language and to read American newspapers and magazines in order that no suspicion would be directed to them in the event they were interrogated while in the United States.
On June 13, 1942, John C. Cullen, a Coast Guardsman from a station in Amagansett, New York noticed Colonel Dasch and three others posing as fisherman off the coast of Long Island with a raft. When the soldier investigated, he found that the men were armed and also noticed a submerged submarine. The men offered him a $260.00 bribe to keep the information of their whereabouts undisclosed. He took the bribe, then alerted his superiors. Investigations later found that the men had left explosives, timers, blasting caps, incendiary devices, cigarettes and German uniforms at the scene. The submarine, however, had since been removed.
It was then confirmed that Nazis had landed on American soil. President Franklin D. Roosevelt and the Federal Bureau of Investigation (FBI) director, J. Edgar Hoover were immediately alerted, and the FBI went on a massive manhunt for the men. Hoover also ordered that all information remain undisclosed to avoid public panic and to not alert the German spies that there was investigation pending.
George John Dasch had been at odds with the Nazi regime. He eventually talked to one of his compatriots, a naturalized German citizen named Ernst Peter Burger, about defecting to the United States. Their original plan was to surrender immediately to the FBI; however, officials disregarded Dasch and Burger’s stories. In order to prove collaboration with the Nazis, Dasch poured $84,000 cash on the office desk of D.M. Ladd, the director of the Domestic Intelligence Division. Dasch was arrested, and interrogated for eight days. Dasch immediately disclosed the whereabouts of all other men connected in the sabotage operation, including Burger. The two vital goals of the sabotage program were to disrupt war industries and to launch a wave of terror by planting bombs, grenades etc. into railway stations, department stores and public places.
President Harry S. Truman after the war had both Burger and Dasch deported back to Germany. There, they were branded as traitors to Germany, responsible for the deaths of their comrades. Both died still waiting in vain for the pardons which had been promised them by FBI Director Hoover.