The Type XIV U-boat was designed to supply other U-boats,[2] being the only submarine tenders built which were not surface ships. It was nicknamed in German the "Milchkuh/Milchkühe (pl.)" (English: milk cow).[3]
Design
The Type XIV was based on the Type IXD long-range U-boat design, but with a shorter and deeper hull. The boats had a displacement of 1,688 tonnes (1,661 long tons) when at the surface and 1,932 tonnes (1,901 long tons) while submerged. The U-boats had a total length of 67.10m (220ft 2in), a pressure hull length of 48.51m (159ft 2in), a beam of 9.35m (30ft 8in), a height of 11.70m (38ft 5in), and a draught of 6.51m (21ft 4in).[1]
Since the cargo of Type XIV was mainly lightweight fuel, it was possible to assign more weight to the pressure hull, and instead of the usual 18.5mm (0.73in) thick steel, 21.5mm (0.85in) was used which resulted in a higher maximum diving depth of 240 metres (790ft).[1][4]
The submarines had a maximum surface speed of 14.4–14.9 knots (26.7–27.6km/h; 16.6–17.1mph) and a maximum submerged speed of 6.2 knots (11.5km/h; 7.1mph). When submerged, the boats could operate for 120 nautical miles (220km; 140mi) at 2 knots (3.7km/h; 2.3mph); when surfaced, they could travel 12,350 nautical miles (22,870km; 14,210mi) at 10 knots (19km/h; 12mph).[1]
Due to its large size, the Type XIV could resupply other boats with 613t (603 long tons) of fuel, 13t (13 long tons) of motor oil, four torpedoes,[6] and fresh food that was preserved in refrigerator units. In addition, the boats were equipped with a small bakery in order to provide the luxury of fresh bread for crews being resupplied. The Type XIV also had a doctor and medical facility for injured sailors, and even had a two-man brig to imprison sailors awaiting discipline back at home. Type IXC boats otherwise only carried 12 weeks of food supplies, and a Type VIIC U-boat carried about 114 tons of diesel fuel.[7][8]
Cargo was transported by means of a 6-metre (20ft) inflatable boat and portable cranes. The flat main deck with cargo hatches and davits was designed in theory to facilitate the transfer of bulk supplies, however its low freeboard made this work extremely hazardous in typical North Atlantic swells that made the deck awash, so often supplies had to be hand-lifted through the smaller but drier conning tower hatches to avoid flooding the boat. Resupply and refueling operations often took hours, putting both the milk cow and the submarine it was servicing at risk.[7]
If the Germans came under Allied attack during a resupply operation, the milk cow would dive first while the attack submarine might fight it out on the surface for a while, as the Type XIV's bulk and flat deck made it slower to maneuver and submerge, although it could dive deeper than Type VIICs or IX.[7] The Type XIV had no torpedo tubes or deck guns, only defensive armament of anti-aircraft guns.[1]
The milk cows operated 300–400 miles (480–640km) off the North American mainland in the so-called mid-Atlantic gap, far enough from Allied anti-submarine patrols and land-based aircraft while still close enough to provide logistical support to U-boats.[7] In 1942, the milk cows enabled Type VIIC boats to remain on station for a couple more weeks off the American coast during the "Second Happy Time" raids of the Battle of the Atlantic.[7]
The milk cows were priority targets for Allied forces, as sinking one milk cow would effectively curtail the patrols of a dozen attack U-boats and force them to return home for supplies.[7]Ultra intercepts provided information concerning sailing and routing of the milk cows. This intelligence, coupled with improved Allied radar, air coverage, and hunter-killer groups in the North Atlantic, eliminated most of the milk cows during 1943 including four lost in the month of July alone. By the end of the war all ten had been sunk. Milk cow duty was especially hazardous; 289 sailors were killed out of an estimated complement of 530–576 men.
Losses during 1943
On 24 July, U-tanker U-459 was destroyed two days out of Bordeaux.[9][10]
On 30 July, three U-boats, two of them Type XIVs, were attacked and destroyed by aircraft of the RAF and ships of FJ Walker's2nd Support Group.[11][12]
On 4 August, U-489 was sunk south of Iceland.[13][14]
U-459, commissioned on 15 November 1941, scuttled on 24 July 1943
U-460, commissioned on 24 December 1941, sunk on 4 October 1943
U-461, commissioned on 30 January 1942, sunk on 30 July 1943
U-462, commissioned on 5 March 1942, sunk on 30 July 1943
U-463, commissioned on 2 April 1942, sunk on 16 May 1943
U-464, commissioned on 30 April 1942, scuttled on 20 August 1942
U-487, commissioned on 21 December 1942, sunk on 13 July 1943
U-488, commissioned on 1 February 1943, sunk on 26 April 1944
U-489, commissioned on 8 March 1943, sunk on 4 August 1943
U-490, commissioned on 27 March 1943, sunk on 12 June 1944[1]
Fourteen planned Type XIVs were cancelled. Three of them (U-491, U-492, U-493) were about 75% complete when work was stopped in 1944. The other eleven boats had not been laid down when they were cancelled on 27 May 1944. On that same day Karl Dönitz stopped construction on the Type XX U-boats, large transport boats that would not have been ready until mid-1945.[1]
