One way ships attempted to avoid enemy torpedoes was through steering in wide angles rather than a straight line, thereby making it difficult for U-boats to aim. For convoys, however, zig-zagging created its own risk, as ships occassionally collided while trying to evade submarines. In his instructions to convoys, RAdm. Albert Gleaves, Commander of the Cruiser and Transport Force, provided detailed diagrams of proper zig-zag maneuvers. This is the first of these diagrams.
"Regulations and Doctrine Governing the Movement of Troop Convoys," DNA, RG 45, Entry 517B.