2019 isn’t the 75th anniversary of the end of the war but on the 6 June it is the 75th anniversary of the momentous action which led to the defeat of Nazi Germany and thus the end of World War 2 in Europe; D Day, writes historian Mark Muller.

Remote Pembrokeshire featured more and more in active participation as the war progressed, perhaps most notably in the numerous airfields that were built to counter German submarine action in the Atlantic.

Some of them are still very visible, but what isn’t so visible, or evident, or perhaps even known about is the huge exercise that was a rehearsal of D Day and which took place on Pembrokeshire’s beaches in 1943.

It had been noticed that many of Pembrokeshire’s beaches were very similar to the beaches and coast of Normandy where the invasion of Europe was to take place and one year ahead of that action, many thousands of soldiers participated in a dummy run for fourteen days in July and August 1943.

The ultra secret operation had the name of ‘Jantzen’. It was to practice ‘Beach Group Organisation’, the ‘Development of a Force Maintenance Area’ and trying ‘Various methods of loading and unloading coasters’.

Additionally there was to be the ‘Construction of an advanced landing ground’ and a practice of the mass movement of troops from where they had been concentrated to embarkation points. An amphibious invasion of the magnitude of D Day had never been done before and it was felt necessary to see a trial in action and find any problems before launching it for real.

Maps and extremely detailed plans are viewable in the County Archives (considerably more than is available online) but which are still marked ‘not for copying or photographing’.

They show that embarkation ports and thus ‘friendly’ loading points were to be Port Talbot, Swansea and Tenby. The beaches on which the ‘invasion’ landings were to be enacted were in a line stretching east from Tenby; Saundersfoot, Wisemans Bridge, Amroth, etc.

These all had code names as the Normandy beaches were to have in one year’s time but instead of Utah, Omaha, Gold, Juno and Sword, these were named, X-ray, William, Victor, Uncle, Tare and Sugar.

There is some confusion amongst reports and descriptions of the exercise, and a few suggest that up to 100,000 men were used in the rehearsal but there were actually very considerably fewer. It seems likely that between five and ten thousand men were used but far more were always being ‘imagined’ as being part of the operation.

The object was to process large numbers of men on to ships and to, not only get them and their equipment unloaded under imaginary enemy fire, but also to trial the logistics involved in unloading sufficient stores and ammunition and vehicles to maintain those troops.

John Tipton of Tenby Museum, in a detailed description of Tenby’s wartime experiences, written nearly forty years ago provides us with some statistics; 35 coasters were used of between 80 and 1500 tons, flotillas of landing craft and landing barges. Sixteen thousand tons of supplies were unloaded during the exercise and an engineer element of the landing force were detailed to penetrate inland as far as Tavernspite and Narberth and amongst other things, construct an emergency landing strip, which they did between Whitland and Tavernspite in less than 48 hours. For all of this to happen there had been huge preparations including extra security. Control points were set up well in advance and civilian movements were monitored and restricted as well as a curfew. The exercise came to an end on 5 August with the awkward realisation that it had not been at all realistic. The only ‘enemy’ had been umpires on the beaches making general, sweeping suppositions as to the potential number of casualties and once ashore, guerrilla type ‘attacks’ with blank ammunition were effected by Home Guard units. But there were even more basic and extremely fundamental problems that came to light.