Top Secret – Tenby’s role in ‘D’ Day

The 6th June 1944 was designated ‘D’ Day, the day 75 years ago when the allied forces landed on mainland Europe to commence the liberation of the occupied countries. Eleven months earlier Tenby had hosted a ‘top secret’ military exercise – Exercise Jantzen.

Jantzen was part of the extensive preparation and planning for Overlord. It took place in Carmarthen Bay between 22 July and 5 August 1943. It was the first exercise undertaken to practice landing on an enemy beach and unloading supplies. The War department filmed the exercise and produced a short film classified as ‘top secret’ that outlined the objective of the exercise and evaluated its success or failure. Fortunately the film (transferred to DVD) survives and Tenby Museum & Art Gallery has a copy in its archives.


During the exercise security in the area was strictly implemented. Entry into the designated area that included Tenby and Saundersfoot was denied to all non residents unless they had a special pass. Tenby was placed under a curfew and the carrying of cameras, telescopes or binoculars was forbidden. All civilians had to carry their identity cards at all times. The curfew from dusk to dawn was in operation from 12 July to 9 August. Mail, telegraph and telephone lines were subject to censorship during this period.

Departure points from friendly territory were represented by Port Talbot, Swansea and Tenby. A number of photographs taken at the time appeared after the war showing the Landing Barges (vehicle) in Tenby harbour being loaded with troops and equipment. Enemy territory was represented by the beaches from Pendine to Saundersfoot. The weather during the exercise ranged from calm to gale force eight.

The evaluation of the exercise concluded that the exercise failed to fulfill its objectives. Equipment failures were common with one barge leaking significant amounts of petrol on Saundersfoot beach. The Alligators used to unload the beached vessels all eventually failed and perhaps most significantly the amount of stores unloaded fell well short of the target set.

The exercise was however a very useful learning curve. Lessons were learned about the loading of supply ships and the need for beach tracking was clearly demonstrated. Similar exercises were carried out on the south coast and ten months later, 6th June 1944, the ‘D’ Day landings took place.

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