n air–gap.
The E-boats lay up in the shelters during the day, safe from air–attack, and put to sea under cover of night to attack Allied shipping. The pens were priority targets after D-Day as the torpedo boats they protected were a considerable threat to the supply lines serving Allied forces in western Europe and were subjected to repeated air attack. This included four attacks by No. 9 Squadron and No. 617 Squadronof the Royal Air Force, during which a total of 53 of the five–ton, Tallboy earthquake bombs were dropped. There were also two attacks in 1945 by the American air force with rocket–powered Disney bombs, specialist weapons designed to penetrate fortified, concrete bunkers that could resist conventional bombs.
The story of IJmuiden during the war is told in the Bunker Museum IJmuiden (Dutch)
