Did other World War II navies need heavily protected submarine pens like Germany's?
Short answerThey needed bases, but not usually comparable pens; local methods such as submerging boats and using existing fortifications could reduce vulnerability.
NotesOther navies maintained submarine harbors but generally did not reproduce the German pen system. At Malta, Royal Navy submarines could submerge during daylight while personnel and technical facilities used older harbor fortifications built to withstand artillery. German pens protected both boats and the vulnerable infrastructure needed to support them. Hardening the base also allowed Luftwaffe aircraft and anti-aircraft guns to be assigned elsewhere. The investment reduced the forces needed to defend a submarine base continuously.