Submarines operating near ports could exploit merchant routes that converged on predictable coastal approaches. Germany's stronger First World War results owed something to this geography and to the limited Allied escort infrastructure then available. Commonwealth yards expanded to build Flower-class sloops, creating an industrial base that later supported the much larger Flower-class corvette program of the Second World War. Hunter-killer groups and patrol aircraft could then push submarines farther from ports, buying convoys more room in which to maneuver and organize their defense.
Notable Point · 52:15-54:25
How coastal convoy geography and shipbuilding shaped the submarine contest
Fixed approaches favored coastal submarines, while First World War escort construction created infrastructure that later supported mass convoy defense.