Tenby, Saundersfoot, and the Secret Rehearsal for D-Day

On this Armistice Day, as we pause to honour the sacrifices of so many, it’s worth reflecting on the crucial but lesser-known role that Tenby and Saundersfoot played in the build-up to D-Day. Nearly a year before the 6th of June 1944, our quiet seaside towns were the stage for a top-secret military exercise known as Exercise Jantzen. It was part of the meticulous planning for Operation Overlord — the allied invasion that would turn the tide of the war.

Exercise Jantzen: A Secret Rehearsal in Carmarthen Bay

From the 22nd of July to the 5th of August 1943, Exercise Jantzen unfolded in Carmarthen Bay, the first large-scale practice landing designed to simulate the challenges of D-Day. With tight security measures, the area around Tenby and Saundersfoot was locked down: non-residents needed special passes, locals had to carry identity cards, and the use of cameras or binoculars was strictly forbidden. It was a level of secrecy that hinted at the importance of what was taking place.

Departure Points and Enemy Beach Simulations

Departure points from Port Talbot, Swansea, and Tenby acted as launch sites from friendly territory, while the beaches between Pendine and Saundersfoot represented the enemy shoreline. It’s hard to imagine now, but those peaceful sands once saw a flurry of military activity. Landing barges filled the harbour, soldiers and vehicles poured ashore, and the noise of engines and shouted orders filled the air.

Lessons Learned From a Challenging Rehearsal

The exercise wasn’t without its difficulties. Equipment failures were common — one barge even leaked petrol across Saundersfoot Beach. The amphibious vehicles, known as ‘Alligators,’ struggled and eventually failed, and the overall volume of supplies unloaded was far below target. Despite this, Exercise Jantzen was a vital learning curve. It highlighted the need for better beach tracking and gave planners crucial insights that would be used to refine tactics for the D-Day landings.

Reflecting on Sacrifice

As we look back on Exercise Jantzen today, it’s important to remember not just the lessons learned, but also the men who took part — many of whom would go on to the real landings in Normandy, never to return. The grainy black-and-white photos and old film reels capture moments of preparation and camaraderie, but behind those images are the faces of soldiers who paid the ultimate price.

Experience the History: Watch the Original Film

Today, we’re fortunate that the original War Department film documenting Exercise Jantzen has survived. Classified as ‘top secret’ at the time, this footage can now be seen at the Tenby Museum & Art Gallery, providing a rare glimpse into the exercise that helped shape D-Day preparations.

If you’d like to delve deeper, you can watch an edited four-reel version from the Imperial War Museum, complete with commentary and animated maps detailing the operations on the Pembrokeshire coast.

👉 Watch the Landing Exercises Here

So next time you find yourself walking the beaches of Tenby or Saundersfoot, take a moment to reflect on the soldiers who trained here and think of those who didn’t make it home. The quiet sands and gentle waves hold memories of a time when these shores were part of something far greater — a chapter of history that helped bring peace to a war-torn world.