At 1030 Local Time on September 10th, 1940 the Canonesa set out from Sydney, Cape Breton to the UK, under the command of Captain F. Stephenson, as part of an 11-ship convoy. She had joined the convoy at Sydney from Montreal and was bound for Liverpool. Her cargo consisted of 7,265 tons of refrigerated and general goods, including 2,258 tons of Canadian bacon, 955 tons of cheese, 250 tons of ham and 379 tons of fish.2 She had a crew of 62 plus one gunner.
On the 11th she joined with a 21-ship convoy which had left Halifax, Nova Scotia at 1430 hours on September 9th. One day later one ship left to return to Halifax but a further eleven joined, coming from South American ports via Bermuda. The 42 ships of Convoy HX72 formed into nine columns, led by the steamer Tregarthen, under Commodore H.H. Rogers. Local escorts were the Royal Canadian Navy destroyer H.M.C.S. Saguenay and patrol vessel H.M.C.S. French3, with the ocean escort being the only escort ship that could be spared for the American leg of the crossing, the armed merchant cruiser H.M.S. Jervis Bay. Canonesa was the second ship in the fifth (i.e. the middle) column - almost in the centre of the convoy and directly behind the Tregarthen.4 Not until they were 400 miles west of Ireland would the merchantmen be chaperoned by destroyers of Western Approaches Command. With the Jervis Bay unable to provide escort cover until the destroyers met the convoy there would, therefore, be a critical gap in mid-Atlantic when the convoy would be unescorted. (It was not until the summer of 1941 that inward convoys from Canada were escorted for the entire duration of the passage.)5
On the 18th the convoy ran into a fresh north-westerly gale. Havoc was caused within the convoy
"as the ungainly merchantmen rolled and yawed wildly, the more heavily-laden ships resembling half-tide rocks as the rising seas broke clean over their exposed decks. Station keeping was impossible, and gradually the orderly ranks of the convoy drifted into chaos. Lifeboats, swung out in readiness for a quick evacuation if a torpedo struck, were smashed, cargoes shifted, and a number of ships fell astern."6
With one ship losing touch the convoy was down to 41 ships when it was sighted late on 20th September 1940 by the German submarine U 47, captained by the U-boat commander Günther Prien. Prien had become a national hero following his audacious sinking of the battleship H.M.S. Royal Oak at Scapa Flow in October 1939. U-47 had expended all but one of its torpedoes in attacking Convoy SC2 on September 10th following which it had been detailed for meteorological duties, twice daily sending in vital weather reports to aid German air raids on Britain. It was whilst carrying out these duties that HX72 was sighted. It has been noted that "although the British D/F service could presumably plot the position of this U-boat twice daily, convoy HX72 did not avoid Prien on 20th September"7 and that "it is therefore hard to understand why HX72 was not warned of the danger into which it was steaming."8 Dönitz has conjectured that "at the long distance involved, direction finding did not give a result sufficiently accurate to enable the convoy to take evasive action".9
The sighting took place shortly after H.M.S. Jervis Bay had been ordered to leave to escort a westbound convoy, leaving the convoy, 500 miles west of Ireland, undefended by either air or surface escorts. (The Jervis Bay is pictured here in a photograph taken from the Canonesa shortly before she left the convoy - Click on the image to see a bigger version and more info about the Jervis Bay). There was expected to be a 20-hour gap between the departure of the Jervis Bay at sunset on the 20th and the rendezvous with Western Approaches Command in the afternoon of the 21st. The vulnerability of HX72 was increased by the onset of uncharacteristically mild Atlantic weather - the wind was a moderate south-westerly with isolated showers giving occasional cover and excellent visibility was provided by a full moon. They were "ideal conditions for skulking U-boats, but bad news for the convoy."10 As one corvette seaman later recalled it was a case of ‘heads you win, tails you lose’ for those on the merchant ships during the war - "when the sea was calm the enemy was active: when it was rough the elements were full of their own hazards."11
Prien was instructed by Admiral Dönitz to sail ahead of the ships, reporting their movements, and to await reinforcements. U-43, U-46, U-48, U-65, and U-99 were instructed to take up positions through which the convoy might pass early the following day. During the night the convoy changed course to the southward and adopted a zig-zag pattern, in accordance with Admiralty orders. The convoy, travelling at 7 knots, was slowed down further by this but managed to pass south of the thirty mile wide patrol line which Dönitz had instructed his boats to form. Dönitz then ordered all the U-boats to close in on the convoy and attack. It was the largest number of U-boats concentrated against a convoy to date in the war.12 In the early hours of the 21st September the first torpedo was fired, the start of a concerted action lasting more than 24 hours.
U-99, under Kretschmer, commenced the attack at 03.12 hours torpedoing the motor tanker Invershannon. Fifteen of her crew perished. The U-99 war diary recorded the following :
"0212 Single torpedo from 1350 metres. Direct hit for’ard. Tanker veers away from the convoy and stops, sinking for’ard with fo’c’sle down to waterline. Crew leaving. A coup de grace will probably be required. It emerges that she is the Invershannon (9154 tons)."13
[Note that Kretschmer's diary entry (02.12) differs by one hour from the British account, reflecting the fact that Britain and Germany were in different time bands.]
Despite Rogers’ attempts to escape the danger by changing direction to port, abandoning the zig-zag and increasing speed to 10 knots the U-boats were able to press home their advantage. At 04.19 Kretschmer placed a torpedo amidships on Baron Blythswood which, carrying iron ore, sank like a stone. According to U-99’s war diary :
"0319 Single torpedo at heavily-laden freighter from 580 metres. Direct hit amidships. Ship breaks in two and sinks in 40 seconds. It is the Baron Blythswood (3668 tons), with, as established later, a cargo of iron ore."14
34 men aboard the Baron Blythswood perished. Half an hour after the Baron Blythswood was sunk the Elmbank was torpedoed. Again Kretschmer’s diary entry records the event :
"0347 Single torpedo at the largest freighter from 1,00 metres. Direct hit amidships. Ship veers away and stops with heavy list to starboard. She transmits her name and position by radio. She is the Elmbank (5156 tons)."15
One crew member out of 56 was lost. Kretschmer and U-99 then tried to sink the crippled Elmbank with gunfire, Prien in U-47 also joining in. They were unsuccessful. Kretschmer then put his last two torpedoes into the Invershannon and Elmbank sending both to the ocean floor. Kretschmer then left for home. The attack was not over, though, as other U-boats arrived at the scene. During daylight on the 21st the Blairangus, straggling well-astern of the convoy, was sunk by a torpedo from Heinrich Bleichrodt’s U-48 (set to become the war’s most successful U-boat accounting for 54 merchant vessels) with the loss of 7 of the crew of 34.
Click here to see a Convoy HX72 ships page, which includes a table of those ships lost and damaged, and information about the eventual fates of the surviving ships.
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