<Li> Type U 139, Type U 142, Type U 151, Type UD 1 </Li> <Li> UB coastal torpedo attack boats <Ul> <Li> Type UB I, Type UB II, Type UB III, Type UF, Type UG </Li> </Ul> </Li> <Ul> <Li> Type UB I, Type UB II, Type UB III, Type UF, Type UG </Li> </Ul> <Li> Type UB I, Type UB II, Type UB III, Type UF, Type UG </Li>

How did the allies chose to protect their ships from u boat attacks