D-Day Conundrum

Sixty-seven years ago today, allied forces crossed the English Channel by air and sea, conducting the largest amphibious invasion in history.

The forces landed on the coast of Normandy, not far from Bayeux, from where the Norman forces under William the Conqueror had left in 1066 to defeat the forces of King Harold and conquer England.

By far the two best movies depicting the landings in Normandy are The Longest Day and Saving Private Ryan. Neither movie, however, depicts the most significant technical innovations of Operation Overlord - the Conundrum, Pluto, Bambi, Dumbo and the Mulberries.

As early as 1941, British military and naval planners recognized that the harbors in the pas de Calais would be heavily defended and that amphibious assault would probably not succeed. The solution: artificial harbors constructed using enormous concrete caissons towed across the channel and sunk to form artificial breakwaters. Inside the breakwaters, cargo was to be offloaded onto floating piers.

The greatest challenge, though, was how to provide enough fuel to the forces once they landed. The answer was to invent, manufacture and test an underwater pipeline system, known as PLUTO (Pipe Line Under The Ocean). The pipeline was to be laid by using enormous spools of line (called Conundrum). Once in place, the pipeline would be serviced by camouflaged pumping stations built in great secrecy under the code names Bambi and Dumbo.

Here is a good summary of PLUTO.