No. 5 Group RAF effective squadrons of Bomber Command, personified by No 617 Squadron the "Dambusters", formed from 5 Group aircrew in March 1943. Most of the group's main airfields were around Lincoln, including RAF Scampton. By the end of the war the group had grown to 15 squadrons. The group was noted for its high accuracy bombing, being involved the sinking of the "Tirpitz" in November 1944 and the shattering of the strategic Bielefeld railway viaduct in March 1945. The Group introduced new weapons operationally, including Barnes Wallis's "bouncing" and his Tallboy and Grand Slam "earthquake" bombs. The group was disbanded on 15
No. 618 Squadron RAF changed to converted Mosquito Mk.IVs. The "Highball" device was intended to bounce across the sea until it hit an enemy ship, sank and exploded. Unlike the cylindrical Upkeep weapon used by No. 617 Squadron RAF in Operation Chastise, the "Highball" was more spherical. The Mosquito selected for the conversion work to carry "Highball" was the Mk.IV series II: the work entailed removing the bomb bay doors and equipping the aircraft with specialised carriers enabling them to carry two "Highballs", each weighing 1,280 lb (580 kg), in tandem. The bombs were designed to skip across water and to provide weapon stability