text: Bielefeld, 14 March By mid-March 1945, over  had been dropped on the Bielefeld viaduct in 54 attacks and damage from 17 hits in one raid was repaired in 24 hours. After an abortive attempt against viaducts at Arnsberg and Bielefeld on 9 March the bombers returned on 13 March, when 9 Squadron and 617 Squadron sent 19 Lancasters each against the same targets, two of the 617 Squadron aircraft carrying Grand Slams, escorted by 75 Mustang Mk IIIs (P-51Cs) from 11 Group. The attack at Arnsberg by 9 Squadron was called off after two aircraft bombed and 617 Squadron turned back from Bielefeld after 129 Squadron (Mustang Mk IIIs) reported unbroken cloud all the way to the target. On 14 March, fifteen Lancasters of 617 Squadron, carrying 14 Tallboys and a Grand Slam, all fuzed for 11 seconds' delay, tried again as fifteen 9 Squadron Lancasters made another attempt against the railway viaduct at Arnsberg. The weather was clear to the targets with some cloud around Bielefeld and a haze over both targets. Escorts from 11 Group consisted of 74 Mustang Mk IIIs and 8 (Pathfinder Force) Group provided four Oboe Mosquitos each from 105 and 109 squadrons to mark the targets. A Mosquito of 627 Squadron was present to film the attack.