A new history of the most crucial few months of the Arctic Convoys, when Germany's air power forced the Allies to retreat to the cover of winter. Between spring and autumn 1942, Germany was winning the battle of the Arctic Convoys. Half of PQ-15 was sunk in May, PQ-17 was virtually obliterated in July, and in September 30 percent of PQ-18 was sunk. The Allies were forced to suspend the convoys until December, when the long Arctic nights would shield them.