A Game of Birds and Wolves: The Ingenious Young Women Whose Secret Board Game Helped Win World War II

by Simon Parkin

sending, either to other U-boats or to U-boat headquarters.* Then there was the fact that, after September 1942, the Western Approaches Convoy Instructions, the bible issued to all British escort officers filled with WATU-coined tactics and signals, was published for Canadian and American ships too, under the new title Atlantic Convoy Instructions. This book ensured escort ships from different Allied navies now used the same anti-U-boat signals where, prior to this, the British were just as bemused by the American signal ‘Zombie Crack’ as the Americans were by the British signal ‘Pineapple’.17 Finally, there was the introduction of Hedgehog, a bow-mounted anti-submarine weapon that could spray a volley of mortar rounds directly ahead of the ship, toward a suspected U-boat location. The name derived from the weapon’s appearance: the twenty mortar rounds were bunched together at a near-perpendicular angle, giving the appearance of a hedgehog’s spikes. The projectiles were primed to explode not by fuse but on contact, and entered the war just as the U-boat captains had become adept at evading depth charges. By increasing the strength of U-boat hulls so that they could withstand the pressure at 600 feet, a U-boat captain could now listen on the hydrophones for the roar of a warship overhead, and the telltale splash of the depth charges, and immediately increase to full speed, turning sharply