Convoys HX 229/SC 122

During the Battle of the Atlantic, British merchant shipping was formed into convoys for protection against German submarine attack. In March 1943 convoys HX 229 and SC 122 were the focus of the largest convoy battle of the Second World War. Kriegsmarine tactics against convoys employed wolfpack tactics in nearly simultaneous surface attacks at night. Patrolling aircraft restricted the ability of submarines to converge on convoys during daylight. The North Atlantic winters offered the longest periods of darkness to conceal surfaced submarine operations. The winter of 1942–43 saw the largest number of submarines deployed to the mid-Atlantic before comprehensive anti-submarine aircraft patrols could be extended into that area.

During March, there was a series of fierce convoy battles which became, for the Allies, the crisis point of the whole campaign. One hundred merchant ships in trade convoys HX 229 and SC 122 encountered three wolfpacks of 38 submarines in a single sprawling action, which German radio reported as "the greatest convoy battle of all time" (Die grösste Geleitzugschlacht aller Zeiten). A Royal Navy report later concluded "The Germans never came so near to disrupting communications between the New World and the Old as in the first 20 days of March 1943".

SC 122 was a slow eastbound convoy of 60 ships, routed from New York to Liverpool. (This was during the period when SC convoys were switched from Sydney, Cape Breton, to New York; this was reversed later due to congestion problems there.) It sailed on 5 March 1943, protected at first by one destroyer and five corvettes of the Western Local Escort Force. On 6 March, off Cape Cod, two ships put back to New York due to heavy weather, and on 8 March, another six abandoned the crossing, and put into Halifax.

The convoy pressed on, changing escorts on 13 March off Cape Race. The western local group left, after the Mid-Ocean Escort Force B5 Escort Group joined from St John's. B5 Escort Group consisted of eight warships, led by Commander RC Boyle in the destroyer HMS Havelock, the destroyer USS Upshur, the River-class frigate HMS Swale, the Flower-class corvettes Buttercup, Godetia, Lavender, Pimpernel and Saxifrage, and a trawler as rescue vessel.

HX 229 was also eastbound and sailed from New York on 8 March, with 40 ships and the local escort. A further 34 ships which should have been included were delayed due to congestion at New York; they sailed the following day as HX 229A. The first few days of the convoy were uneventful; HX 229 met its Mid-Ocean Escort Force on 14 March and the local escort departed. The ocean escort was B4 Escort Group from St John's, of four destroyers and a corvette. It was led on this occasion by Lieutenant Commander Gordon John Luther of HMS Volunteer, as its regular leader was in dock for repairs. Luther, although an ASW specialist, had recently joined the group and this was only his second crossing. The other ships of B4 were the destroyers HMS Beverley, Mansfield and Witherington and the corvette Anemone, although Witherington had to detach on 15 March, to be replaced by the corvette Pennywort for the crossing.

HX 229A sailed on 9 March, meeting its ocean escort, 40 Escort Group, on 15 March. This comprised six sloop-type warships under Cdr. J Dalison in HMS Aberdeen. Taking a more northerly route than HX 229, the convoy remained undetected by German patrol lines and made a safe and timely landfall on 26 March. The voyage was not without its perils though. The more northerly route took it into an icefield and two ships were damaged by icebergs, rerouting to Iceland. The convoy vice-commodore's vessel the Svend Foyn was also damaged and ultimately sank on March 19, 1943.

Arrayed against them were three patrol lines (rakes) of U-boats:

The German B-Dienst signals intelligence group had given notice of an east-bound convoy and by 8pm on 13 March had a location for SC 122. Admiral Karl Dönitz, commanding the U-boat fleet, directed Raubgraf to intercept, forming a new rake to the west. A westerly gale gave speed to SC 122, which passed through Raubgrafs patrol area on the morning of 15 March just 24 hours before the patrol line was formed.