By Cmdr. Michael Kidd, SC, USN

The problem of delivering logistics support in contested environments keeps military leaders up at night! Stealth Combat Logistics Force (CLF) ships and submerged caches of war materiel are the providence of today’s war planners and logistics futurists. These are not new ideas though; more than 70 years ago logisticians from the German navy launched their own submerged logistics fleet.

Aggressive employment of U-boats during the Second World War threatened to cut the flow of war materiel not only from the new world to Europe, but also along the eastern seaboard of the United States. For months in 1942, unopposed attacks on merchant hulls, known as the German’s “Second Happy Time”, sent scores of ships with hundreds of thousands of tons of oil and materiels to the ocean bottom. Less appreciated, is how German diesel submarines were able to maintain time on station in contested areas without a robust surface replenishment fleet or friendly ports.

The Milk Cow (Type XIV submarine) was a 220 foot, 1,688 ton vessel, capable of transporting 603 Long Tons of diesel, 13 Long Tons of motor oil, 4 torpedoes, and fresh food to forward contested environments. Operating off the East Coast of the United States, South Africa, and in the North Atlantic – they supported deployed U-boats with fuel and provisions, permitting significantly expanded time on station.

For the German U-boats to operate off the U.S. Coast, they used 5,000 miles of their 6,500 fuel endurance transiting to and from station, leaving little time left to patrol. The Milk Cows embarked external fuel tanks which they used to transfer fuel to other U-boats on the surface, along with weapons, medical services, and even fresh bread – submerging afterwards to maintain their covert posture. Of the ten Type XIVs deployed, they provided a combined 437 refueling missions between March of 1942 and June 1944. They permitted German U-Boats to extend their on-station time between four and eight weeks, depending on the class of boat.

It was widely understood by combatants on both sides of the conflict that the Milk Cows were a critical requirement in what military historians identify as the Clausewitzian Center of Gravity of Hitler’s war machine; his U-boat fleet. Admiral Dönitz, who led Germany’s undersea warfare efforts planned for 14 additional boats, recognizing their effectiveness in extending the warfighting reach of the fleet in the 1942 and 1943. As the Allied technological advances and ability to capture German signal transmission increased, it became clear that they were no longer able to resupply with impunity and Dönitz canceled the remaining boats. Though it may not have countered the Allied onslaught and saved the Milk Cows, of interest is that the Germans had outfitted one of the last surviving boats with equipment to transfer fuel while submerged, to limit their most vulnerable time exposed on the surface. U-490 was sunk by allied destroyers on June 11th , 1944, before being able to prove the new capability. During the waning days of the battle of the Atlantic, U-boats being serviced by the Milk Cows would accept great peril, remaining surfaced to engage attacking Allied ships or planes in order to permit their suppliers extra time to submerge to safety. Their significance was not lost on the Allies. At the tactical level, pilots would ignore attack submarines in order to mount an attack on a surfaced Milk Cow, and at the operational level; the Allied Naval Headquarters order to “Get the Milk Cows at any cost,” was attributed directly to the English Prime Minister, Winston Churchill.

Today’s logisticians would be well advised to leverage the experience of their German predecessors while planning future combat capabilities. The most significant weakness of the Milk Cows was that they were vulnerable on the surface, as they were big and slow to submerge when Allied ships or aircraft located them. As Allied nations developed new surface search radars capable of identifying surfaced submarines, allied forces were able to rapidly attrite the German Milk Cow fleet. As with any key capability, it is important to take protection of these assets into account as part of the deployment strategy. Should today’s logistics futurists field stealth caches to solve the problem of sustainment in contested environments, it is imperative that they are protected in such a way that enemy forces cannot take them away. The rapid rise and fall of the Milk Cow fleet, and the lessons applied to today’s problem sets demonstrated the need for leaders at every level to be educated on historic experiences of the past in order to shorten the learning and development cycle for emergent systems and strategies.