March 1943 — where to place the escorts?

In the basement of Derby House in Liverpool, where the Battle of the Atlantic is tracked hour by hour, March 1943 looks like catastrophe: 120 ships sunk in a single month. 'The Battle of the Atlantic was the dominating factor all through the war,' Churchill would write; never for a moment could one forget that everything else depended on it. And the scales are tipping the wrong way.

Yet new tools are at last pouring in: very-long-range aircraft fitted with radar and Leigh Lights, high-frequency direction-finding, forward-firing mortars, and the German cipher traffic readable once more. What remains is to decide how to use this windfall. One long-unloved officer has argued for years that the Navy should stop clinging to its convoys and go strike the enemy at his own door.

The staff can keep every escort in close defence, welded to its convoy as caution has always demanded; it can detach independent support groups, hunter-killers free to chase the U-boats wherever they are; or bet first on very-long-range aircraft and the sealing of the Bay of Biscay, through which the packs reach the open sea.