The wolfpack idea belonged to Karl Donitz, commander of Nazi Germany's U-boat arm. He had spent the interwar years arguing that submarines, working in coordinated groups, could break the convoy system that had eventually starved his side's commerce raiders in the First World War. The early attempts failed. Through the first nine months of the Second World War, U-boats stayed with the familiar pattern of solo patrols. Then, with the Norwegian campaign winding down in May 1940 and France collapsing, Donitz tried again. Two consecutive June patrols were dispatched as concentrated formations - Rosing's group off Cape Finisterre, then the boats later grouped under Prien's name. The historian Clay Blair, working through the same records, would later read these as a series of individual sorties dressed up as a pack. Others - Rohwer, Showell, the uboat.net database - kept the wolfpack label. The disagreement matters because doctrine was being argued in real time, with ships and lives the testing material.

The seven submarines listed by Rohwer were U-25, U-28, U-30, U-32, U-38, U-47, and U-51. Their target was convoy HX 47 - merchant ships steaming from Halifax in Nova Scotia toward Liverpool, carrying the food, fuel, and war materiel that kept Britain in the war. German naval intelligence had detected the convoy, and between 12 and 15 June the U-boats moved into position across the approaches south of Ireland. The plan was theoretical pack tactics in practice: multiple boats finding a convoy, then attacking together to overwhelm the escorts. What actually happened was less coordinated. Only two of the seven boats - U-38 and U-47 - ever made contact with HX 47, and they attacked separately rather than as a pack. The remaining boats prowled their assigned sectors, picking off whatever solo ships or strays they encountered. By 17 June the formation had dissolved and the boats were turning west of the Bay of Biscay, heading back to occupied French ports.

Five vessels went down. On 13 June, U-25 fired a torpedo into the stern of HMS Scotstoun, an armed merchant cruiser - a converted liner pressed into wartime service - about 80 nautical miles west of Barra in the Outer Hebrides. A second torpedo ten hours later sent her down by the stern, and seven of her crew were killed. The following day, in attacks south of Ireland, U-47 hit the Balmoralwood, a straggler from HX 47, about 70 nautical miles south-southwest of Cape Clear; her master, 39 crew, and a gunner were picked up by another ship in the convoy. On 14 June U-38 surfaced and shelled the Mount Myrto with 53 rounds before a torpedo struck her, but the timber she carried kept her afloat. The next day U-38 returned to the convoy and sank both the Italia and the Erik Boye within four minutes, the torpedo into Italia's engine room killing nearly all the men working there. Survivors were picked up by HMS Fowey. These are accounting facts; the deaths inside them - merchant sailors, men in engine rooms, men in the freezing North Atlantic - are what convoy battles actually were.

If most reliable sources do not call it a wolfpack at all, why does the term persist? Partly because it was useful to the Germans: the dramatic name signaled doctrine working as designed. Partly because Gunther Prien himself was a propaganda figure - the man who had slipped U-47 into Scapa Flow in October 1939 and sunk the battleship Royal Oak with the loss of 835 lives, and whose own death in March 1941 would be hidden from the German public for weeks. The Battle of the Atlantic had not yet reached its terrifying mid-war peak in June 1940. The convoy escorts were thin, the radar primitive, the codebreakers on both sides still finding their footing. What happened south of Ireland that week was an experiment in tactics that would, by 1941 and 1942, evolve into the genuine wolfpacks that nearly choked Britain into surrender.