Mulberry and Pluto are often unfairly characterised as a British-only invention but US forces also bought a couple of their own important innovations to D-Day logistics.
The Rhino ferry consisted of a number of steel pontoons connected with steel straps and angle sections that could be formed into pontoons or causeways. The complete assembly was powered by two 60-horsepower engines, as can be imagined, they were woefully underpowered. The top speed when loaded was 3 knots and in the poor weather, they were unmanageable.
However, 36 Rhino ferries were used on Utah and Omaha beaches, towed across by LST. They were joined by 12 causeway tugs, 12 warping tugs, 2 floating dry docks and a couple of repair barges.
They were also used on the British and Canadian beaches to good effect. To reduce the need for the LSTs to the beach, vehicles drive off the LST and onto a Rhino ferry before the ferry preceded to the beach. This protected the valuable LSTs from the threat of mines in the surf zone until completely cleared and from direct fire during initial landings.
Despite their susceptibility to poor weather, they provided sterling service throughout the period as both ferries and causeways.
The second major US innovation was the DUKW.
The DUKW became indispensable because not only could they ferry stores to the beach they could take them directly inland to the numerous dumps.
This factor alone meant the DUKW should be considered a war-winning vehicle.
Whilst Mulberry was being built, LSTs and DUKWs also did sterling work but the DUCKs could not unload large stores, bridging equipment for example, and the LSTs, once beached, had to wait for the tide to re-float.
LSTs also had problems with heavy vehicles and artillery because the sand was unable to bear its weight without significant and time-consuming reinforcing.
Discharging at a Mulberry LST pier took on average, 64 minutes, compared with several hours when discharging onto the beach. It is fair to say, the DUKW was the unexpected superstar of D-Day because they could take their loads directly inland to store dumps without creating a disorganised collection of boxes and jerry cans on the beach.