Why convoys needed Flower-class critical mass

The Flower class was built to hunt submarines and keep U-boats away from merchant ships. Of 294 corvettes, 33 were lost during the Second World War and 22 of those losses were credited to submarines, figures that frame how poor an exchange an escort could impose. A submarine that attacked a small, replaceable corvette spent torpedoes and exposed itself instead of striking valuable cargo. On the surface, the corvette's four-inch gun and lighter weapons made a direct fight especially dangerous for a pressure-hulled U-boat. Convoy strategy therefore depended on procuring enough capable escorts because a few individually impressive ships could not cover the traffic.