Winston Churchill had predicted the Arctic Convoys would be "the worst journey in the world". The biggest disaster in naval history befell Convoy PQ17.
The convoy left Iceland on 27 June 1942 for Arkhangelsk made up of 36 merchant ships and six naval auxiliaries with one close and two distant escorts, 43 warships in total. The convoy was carrying 297 aircraft, 594 tanks, 4,246 trucks and trailers, and 150,000 tons of military and general supplies. It was by far the largest convoy ever to sail to Russia.
The biggest threat to the Royal Navy at the time was the German battleship Tirpitz, armed with a main battery of eight 15-inch (38 cm) guns in four twin turrets. She had been deployed to Norway in January 1942 in order to prepare to attack a convoy.
In March 1942, the Tirpitz launched her first attack on PQ12 convoy, but bad weather kept her from zeroing on the convoy and the attack failed. Later, the German navy, the Kriegsmarine, came up with Operation Rösselsprung (Knight's Move), a plan to bring the Tirpitz and her entourage into contact with the next outbound convoy PQ17.
On 4 July after sending a message from Norway to the Admiralty in London, saying that the Tirpitz has moved the previous day, the First Sea Lord Sir Dudley Pound, fearing attack, commanded the escort ships to turn back and the convoy to scatter and to chart their own course to Russia.
It was a mistake of historic proportion that profoundly misjudged the situation and would have fatal consequences. The Tirpitz has merely changed position to the north without any plans to intercept the convoy.
Fully exposed to Nazi aircraft and U-boats without any escort, PQ17 was gradually destroyed. By 22 July only 11 of the convoy's original 36 merchant vessels had reached Arkhangelsk, delivering just 70,000 tons - less than half the anticipated cargo.
In his monumental six-volume record of those times, The Second World War, Churchill called PQ17 "one of the most melancholy naval episodes in the whole of the war." U.S. Admiral Dan Gallery in his memoirs was more blunt, referring to the disaster as "a shameful page in naval history."