On 31 December 1942, German surface forces tried to destroy Convoy JW 51B as it carried supplies toward Kola Inlet in the Soviet Union. One attacking group would draw the close escort away while another approached the merchants from the opposite direction. Italian forces had already used similar tactics against British convoys in the Mediterranean, so the idea was familiar to the Royal Navy. British convoy doctrine made the merchant ships the priority and assigned the pursuit of attackers to separate supporting forces. Keeping that division of responsibility mattered more than chasing an opportunity to sink an enemy ship.
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Why protecting Convoy JW 51B mattered more than chasing the enemy
The British defense separated close escort from covering forces so destroyers could remain fixed on the convoy while cruisers dealt with surface raiders.