When leaving Gibraltar on 17 September:
British destroyer HMS Vimy (D 33) (LtCdr H.G.D. de Chair, RN) until 22 September
British escort destroyers HMS Duncan (D 99) (LtCdr A.N. Rowell, RN) and HMS Farndale (L 70) (Cdr S.H. Carlill, RN) until 20 September
British sloop HMS Fowey (L 15) (LtCdr L.C.A. Leefe, RN)
British corvettes HMS Begonia (K 66) (T/Lt T.A.R. Muir, RNR), HMS Gentian (K 90) (Cdr R.O. Yeomans, RD, RNR), HMS Hibiscus (K 24) (LtCdr C.G. Cuthbertson, RNR), HMS Jasmine (K 23) (LtCdr C.D.B. Coventry, RNR (retired)), HMS Larkspur (K 82) (Lt S.C.B. Hickman, RNR), HMS Myosotis (K 65) (Lt G.P.S. Lowe, RNVR), HMS Periwinkle (K 55) (LtCdr P.G. MacIver, RNR) and HMS Stonecrop (K 142) (Lt J.V. Brock, RCNVR)
British fighter catapult ship HMS Springbank (Capt C.H. Godwin, DSO, RN (retired)) until lost on 27 September.

Joined on 20 September: British destroyer HMS Wild Swan (D 62) (LtCdr C.E.L. Sclater, RN) until 22 September
Joined on 22 September: British destroyer HMS Highlander (H 44) (Cdr S. Boucher, RN) until 26 September
Joined on 28 September: British destroyer HMS Wolverine (D 78) (LtCdr J.M. Rowland, RN)

* U-boats that fired torpedo or used the deck gun

One day after the convoy HG-73 had left Gibraltar, a German Fw200 Condor aircraft (KG 40) located the ships off Cape St. Vincent but was chased away by the Fulmar fighter from HMS Springbank. Four Italian submarines on patrol west of Gibraltar were ordered to search for it: Leonardo Da Vinci (CC Ferdinando Calda), Alessandro Malaspina (TV Giuliano Prini) *, Morosini (CC Athos Fraternale) and Luigi Torelli (CC Antonio De Giacomo).

On 19 September, the Morosini made the first contact with the convoy but one of the electrical engines broke down and the submarine returned to base. The same day, U-371 sighted the convoy as well but the U-boat was en route to the Mediterranean and ordered to continue its mission. In the evening on 20 September, Torelli found the convoy and was badly damaged by depth charges from HMS Vimy when she tried to attack the convoy during the night of 21/22 September, forcing the submarine to abort its patrol. On 23 September, Da Vinci sighted the convoy again and kept contact for U-124 and U-201 which were directed to it by the BdU, coming from the battle against convoy OG-74. The next day, a Fw200 aircraft located the convoy and sent homing signals.

During the following night, only U-124 reached the convoy and reported unsuccessful attacks on a cruiser sailing ahead of the convoy HG-73, possibly misidentifying the fighter catapult ship HMS Springbank and a destroyer, before sinking the first ship. The U-boat was joined by U-203 the next night and together they sank five ships, while U-201 also reached the convoy but was chased away by the escorts. In the night of 26/27 September, all three U-boats attacked again sinking two more ships and HMS Springbank, while the outbound U-205 made contact but lost the convoy in bad visibility.

On 27 September, Allied flying boats arrived to screen the convoy HG-73 and they kept the most U-boats at distance, only U-201 managed to attack the following night, sinking another steamer. Three of the four participating U-boats were now out of torpedoes and the BdU ordered U-124 and U-201 to return to base, while U-203 shadowed the convoy for U-205, but this U-boat had been bombed and damaged in the evening on 28 September and the operation was broken off at dawn on 29 September.

The three attacking U-boats claimed the sinking of 10 ships with 62.000 tons, one corvette possibly sunk and another ship damaged. This reflects the reappearing problem of overestimating the targets in the Gibraltar convoys, the commanders mistaking coasters with the engine aft as tankers and claiming normal ship sizes for North Atlantic convoys, while the average size of the ships in the convoy HG-73 was about 2200 GRT for example.

On this occasion the cooperation between the U-boats and air reconnaissance of the Luftwaffe worked as intended, the Fw200 aircraft of KG 40 being in contact with the convoy after it left Gibraltar, on 24 and 26 to 28 September, sending homing signals and helping the U-boats to get into a favorable position for the night attacks. Moreover, the Italian submarines were complimented by the BdU for their shadowing work in the early phase of this battle. None of the submarines reported a successful attack on the convoy, but a Fw200 reported two ships in sinking condition and one burning ship behind the convoy on 24 September, so they were wrongly credited to Malaspina * which did not return from her patrol. Allied sources mention no ships being lost or damaged in this area on that day.

* Unknown at this time was that Malaspina had already been lost on 10 September, bombed and sunk with all hands by the Australian Sunderland aircraft W3986 (10 Sqdn RAAF/U, pilot F/L A.G.H. Wearne, RAAF) while outbound in the Bay of Biscay in position 46°23N/11°22W. The submarine was reported missing after leaving Bordeaux on 7 September and for some time it was thought that she had been sunk by the British destroyer HMS Vimy during the night of 21/22 September in the vicinity of convoy HG-73, but this attack was in fact directed against Torelli. Her fate was revised in March 2004 by Dr. Axel Niestlè and Eric Zimmerman.

Reassessment of ships hit from HG-73

See our new article Convoy HG-73: Reassessment of U-boat attacks during the nights of 25/26 and 26/27 September 1941 by Rainer Kolbicz published on 3 Aug 2009.