Wulf Dietrich Christian Schmidt, later known as Harry Williamson (7 December 1911 – 19 October 1992) was Danish citizen who during World War II became a double agent working for Britain against Nazi Germany under the codename Tate. He was part of the Double Cross System, under which all German agents in Britain were controlled by MI5 (British counter-intelligence) and used to deceive Germany. Nigel West singled him out as "one of the seven spies who changed the world."
Career as a double agent
Schmidt was sent to Britain by the Abwehr in September 1940, landing by parachute. He was captured immediately, as a previous captured agent had given away his coming, in return for a promise that Schmidt, a friend, would not be executed. 
Schimdt broke down under interrogation and became a double agent, making contact with Germany by radio in October 1940. He was one of the longest running agents in the Double Cross System: his last contact with Germany was on 2 May 1945. He operated his radio himself until he became ill and had to be imitated by a British operator. Though he recovered, he was not allowed to operate thereafter. He did continue to assist in composing the messages sent to Germany.
Tate participated in many deception and counter-intelligence operations. As a working agent, he needed money. In 1941, the Germans used a Japanese diplomat to deliver some money to Tate, which revealed the extent of German-Japanese cooperation.
In July 1941, the Abwehr sent £20,000 to Britain, which was received by Tate. With this huge sum (about $2,000,000 in 2011 terms), Tate notionally established himself as a rich "man about town" in London, with easy access to black-market liquor and other luxuries. As such, he could plausibly make friends with military officers and civilian officials, and get intelligence from their loose talk, or even recruit them as agents.
At the same time, Tate reported to the Germans that to avoid military service, he was employed on a farm owned by a friend, and could only visit London on weekends. This provided an excuse for his not recruiting more agents or reporting as much as the Germans wanted.
Nonetheless, Tate participated in the Operation Bodyguard deception which covered the Invasion of Normandy. He notionally went to work on a farm near Wye in southeastern England, where the imaginary "First United States Army Group" (FUSAG) was located. Tate provided the Germans with the schedules for rail transport of FUSAG troops to ports of embarkation for the invasion.
This apparent feat was highly regarded in Germany. For this and his other apparent successes, Tate was granted naturalization as a German citizen so he could receive the Iron Cross First and Second Class.
Tate's last deception was in early 1945. German submarines ("U-boats") running submerged or with only the snorkel up could not use normal navigation methods. But they found a way to fix their positions off southern Ireland, where there was a distinctive conical seamount. Using the depth sounder, a submarine could locate the peak of the seamount, which was a known position. Rodger Winn, head of the U-Boat Tracking Room, suspected this and suggested laying a minefield at that spot. No minelayer was available, so he approached the Double Cross team, and suggested telling the Germans through a controlled agent that there was a minefield there.
Tate was chosen, as one of his notional friends was a Royal Navy officer who was a minelaying expert. Tate reported that his "mine-laying friend" had bragged to him about a new minefield near Ireland, with clues that should have alerted the Germans. However, nothing seemed to happen. Then, by coincidence, a U-boat was reported sunk off Ireland. Tate reported that his "mine-laying friend" had come by to celebrate this success. Tate added that he was angry and ready to quit: he risked his life for this intelligence, and a U-boat was lost because the Germans hadn't acted on it. Two days later, the German Navy ordered the U-boats to avoid a zone sixty miles square around that seamount - thus losing that navigation fix, and also providing a safe zone for Allied ships.
- West, Nigel Seven Spies Who Changed the World. London: Secker & Warburg, 1991.
- Masterman, p 88-89
- Masterman, p 259
- Masterman, p 134
- Masterman, p 143
- Masterman, p 131
- Masterman, p 143
- Masterman, p 143
- Masterman, p 228-229
- Masterman, p 88
- Masterman, p 89
- Montagu, pp 174-175
- Montagu, pp 175-177
- Masterman, J. C. The Double-Cross System in the War of 1939 to 1945. Avon, 1972.
- Montagu, Ewen. Beyond Top Secret Ultra. Coward McCann & Geoghegan, 1978.
- Jonason, Tommy; Olsson, Simon. Agent TATE: The Wartime Story of Harry Williamson. London: Amberley Publishing, 2011. ISBN. 1445604817.