The engineering of the port at Arromanches

The German strategy had been to fortify by land and by sea all the ports, expecting if they held the ports they would hold all of Europe.  After the disaster of trying to capture Dieppe, Churchill hatched a plot to build his own harbor that would supply invading troops using a floating road that would float with the tides. 

The port harbor was built in separate pieces in England sailed across the channel the night before the invasion.  Parts were made from concrete due to the lack of steel in Britain. These were used to float the landing platforms and floating roads. 

Along with the parts of the port built in England, they sailed old ships across and then sunk them to start the break wall and to give coverage. The harbor was begun within 1 day of landing and by day 10 was fully functional. Engineers had surveyed the area before the invasion and each block was numbered to know where it was to be placed in the master construction plan. 

No landings were held at this beach to allow for construction. It was as large as 700 football fields! It also had ways to hide the lights using artificial lights and with hydrogen filled balloons that prevented planes from bombing the new harbor. 

For an experimental design never before tried it was an engineering marvel. It even mostly withstood a hurricane force goal 13 days after the invasion. Only 25 of the blocks remain, many having been recycled for the steel, and others having been destroyed.