 On 30 July 1943 Walker's group saw further success when they encountered a group of three U-boats on the surface (two were vital submarine type XIV replenishment boats known as "Milk Cows") while in the Bay of Biscay.He signalled the "general chase" to his group and fired at them, causing damage that prevented them from diving.Two of the submarines, , a Type XIV, and , a Type IX/C40, were then sunk by Walker's group, and the second Type XIV, , by Australian Short Sunderland aircraft.