V3- Hochdruckpumpe

The V3 site at Mimoyecques , France

Only one site was chosen for the Hochdruckpumpe (HDP) , the location a few miles inland between Calais and Boulogne.

In 1943 work started on the site, tunnelling into the hillside from both sides, with the planned length of 450 feet. The main railway line passed nearby.

Rather than being able to move the weapon this was fixed into the hillside. The gun barrels had to be buried underground and only the exit nozzles for the shells would appear above ground

In 1943 French agents reported that a new secret weapon was being built. The RAF wasted no time in bombing the site with 4,100 tons of bombs dropped. This was the heaviest bomb load dropped on any V- site

As a long range weapon, conventional artillery is limited because of the practical limit to the length of the barrel. One solution was to have a very long barrel, over 400 feet in length.

The V3 could fire 500 shells per hour. As the shell moved down the barrel, 28 sequential charges were fired electronically from side branches, each one accelerating the shell from its initial firing velocity in the breech

Originally 25 barrels were planned for the site, set in groups of 5, but by the time construction had started this had been reduced to 15 barrels.

The raid on 6 July 1944 included seven 12,000Ib Tall Boy bombs

Although the HDP never fire a shot from Mimoyecques, the remains of the barrels and other items were moved to Germany

Trains entered the main tunnel at the south entrance at Mimoyecques and unload supplies in the centre and then would be conveyed along eleven 160 feet side tunnels

On the 27 September 1944 Canadian troops found the site intact, but stripped of equipment. On the 9 & 14 May 1945 British Army sappers detonated 36 tons of explosives inside the tunnels.

The HDP project was later rebuilt in Germany, near Trier, on the banks of the River Ruwer. Here two shortened versions of the barrel would target the advancing Allies.

On the 30 December 1944 the first HDP shells were fired towards the  US Third Army in Luxembourg, a distance of 27 miles. Eventually as the Battle of the Bulge came to an end , 22 February 1945 was the last time the V weapon was used  with just over 180 shells fired.

A reincarnated HDP appeared as Saddam Hussein's `super gun', the  580 ft barrel aligned on Israel 500 miles away