United States Army Air Forces, as part of Operation Aphrodite, used US designed and operated radio-controlled aircraft, "Bat" guided bombs. Whereas the RAF Bomber Command, used the Royal Navy designed "Disney" rocket-assisted bombs, and the Barnes Wallis devised Tallboy and Grand Slam deep penetration bombs. A U-boat pen concrete target had been built at Ashley Walk bombing range in the New Forest, Hampshire, to assist in preparation for these raids. It consisted of a concrete roof covering three shallow "pens". After the war it was buried in an earth mound, although its edges are once again visible in places due to weathering. Post war Yugoslavia The Yugoslav People's Army used submarine pens as well, including ones on the islands of Vis and Brač or in Kotor Bay, carved inside natural hills. The ones in Montenegro fulfilled their purpose, housing and protecting the submarines and missile boats from NATO aerial attacks during Operation Allied Force in 1999. They are now abandoned and freely accessible from sea or by foot. See also Muskö naval base (Sweden) Naval museum complex Balaklava (includes several cold war era submarine pens) Yulin Naval Base (China) Notes Bibliography External links German World War II U-boat pens in France Bunkers World War II strategic bombing