Convoy PQ-17 had departed Iceland on 27 June 1942, bound for Arkhangelsk with 35 transports carrying 297 aircraft, 594 tanks, over 4,000 vehicles, and more than 156,000 tonnes of war material desperately needed by the Soviet Union. The summer of 1942 was among the bleakest of the war for the Soviets, and this convoy was as much a political gesture as a military one -- Winston Churchill's War Cabinet authorized it despite enormous risk. German aviation held numerical superiority over the Barents Sea, and the perpetual Arctic daylight eliminated any cover of darkness. A massive escort accompanied the convoy: 19 close-protection warships, four heavy cruisers, an aircraft carrier, two battleships, and a screen of 13 Allied submarines positioned along the routes German surface ships might take.

The German plan, codenamed Rosselsprung -- "Knight's Move" -- called for deploying every available heavy warship in Norway. The battleship Tirpitz, heavy cruisers Admiral Scheer and Admiral Hipper, seven destroyers, and two torpedo boats formed a strike force under Admiral Otto Schniewind. On 5 July, this squadron sortied from its Norwegian fjord anchorage, choosing the western channel past Rolvsoy Island rather than the eastern route prescribed by higher command. Schniewind judged the western passage less exposed to submarines and mines. The British Admiralty, aware the Tirpitz had sailed, made the fateful decision to scatter the convoy. The transports dispersed across the Barents Sea -- and without the protection of their escorts, they were picked off one by one. Twenty-four of the thirty-five ships were sunk.

K-21 was lurking at 20 meters depth when hydroacoustician A. Smetanin detected propeller noise at 16:30. Atmospheric refraction over the Arctic sea played tricks with visibility -- Lunin initially mistook the distant masts of the German fleet for a surfaced U-boat, then for two torpedo boats. Only as the shapes resolved did he recognize the unmistakable silhouette of a battleship. He ordered an attack. The range was enormous -- far beyond what Soviet torpedo doctrine considered effective. At 18:01, K-21 fired two torpedoes from its bow tubes, followed by two more from the stern at 18:04. Lunin then took the submarine deep. Through the hull, the crew heard two explosions, which Lunin logged as torpedo impacts. Unable to observe the results through his periscope, he reported the attack to fleet command.

On 8 July, the Soviet Information Bureau announced that a submarine had struck the Tirpitz with two torpedoes, causing significant damage. Pravda and Krasny Flot published detailed accounts naming Lunin as the hero who had forced the German squadron to abandon its attack on the convoy. In a nation desperate for good news, the story took on a life of its own. But the German records tell a different story. No torpedo impacts were noted on any ship in the squadron. The attack itself went entirely undetected by the Germans. The Tirpitz required no repairs upon returning to port. Five hours after K-21's torpedoes entered the water, the German squadron turned back -- not because of any damage, but because the convoy had already been scattered and the operation's risks outweighed its diminishing rewards. The explosions Lunin heard were likely his own torpedoes detonating at the end of their run.

Lunin was decorated and celebrated as a Soviet hero. For decades, Soviet literature maintained that his torpedoes had struck the Tirpitz. Western historians consistently concluded otherwise, citing the absence of any German documentation of hits or damage. A British-led joint inspection team that examined German naval records after the war found no evidence supporting the Soviet claims. The debate persisted well into the post-Soviet era, with Russian historians gradually acknowledging the likely miss. Yet Lunin's courage was never in question -- he attacked the most powerful surface combatant in northern European waters from a submarine, at extreme range, in Arctic conditions. That the torpedoes probably missed diminishes the propaganda narrative but not the seamanship. These cold northern waters off Finnmark, where the Norwegian Sea meets the Barents, witnessed some of the war's most desperate naval engagements, and K-21's attack remains a defining moment of the Arctic convoy campaign.