After the D-Day invasion of Normandy on 6th June 1944 the next task was to resupply them with food, ammunition, fuel and everything else an Army needs to operate.
But the Allies did not yet have a harbour for ships to unload supplies for distribution to the troops.
It was a problem the Allies solved by taking a harbour with them. The Mulberry Harbours.
The Mulberry Harbours were critical to the success of D-Day. And part of them were built in Rotherhithe.
The Mulberry Harbours were built of many different parts, one of which was the Phoenix caissons. These were huge blocks of concrete that could float. They were towed across the English Channel by tugs to the Normandy beaches were they were to be joined together as a breakwater making the water inside the harbour calm by stopping the waves hitting it.