AAF recognized that more compact formations were needed and returned to the three-aircraft vee formation that had been standard before the war. Squadrons consisted of three such vees, all flying at the same altitude, with two such squadrons in a group formation, the second higher, trailing, and staggered to the right. The entire formation was high, deep, and nearly across. It proved cumbersome to maneuver, as did a 36-plane alternative, and left many bomber gunners with restricted fields of fire. The original two heavy bomb groups of the Eighth Air Force transferred to North Africa and were replaced in October and November by four new groups of B-17s (the 306th, 91st, 303rd, and 305th groups), and two of B-24 Liberators (44th and 93rd BGs), each of which experimented with its own formations. Their early missions included numerous mechanical turnbacks ("aborts") which hampered development of effective schemes. Between November 1942 and the end of the war various configurations of the combat box were adopted to meet changing conditions, particularly changed German tactics that stressed head-on attacks against the weak forward firepower of the bombers. The 305th BG innovated the 18-aircraft "javelin down" formation, which stacked planes within an element and squadrons within a group downwards in the direction of the sun. This aided gunners on the higher aircraft in seeing lower aircraft without being blinded by glare. In the front elevation the formation resembled a set of stairs, but in profile and plan resembled a spear point. Unlike earlier group formations in which the lead bomber had flown in the lowest position, it now was placed in the center of the formation vertically. The 305th successfully tested the formation on a December 6, 1942, mission to Lille, and it was immediately adopted by the other three B-17 groups. The 305th soon developed a more compact staggered formation that stacked elements downward in one direction, but stacked squadrons upward in the opposite direction. A third element of three bombers was added to the 18-plane box, placed in the most exposed squadron for additional support. This resulted in a 21-plane wedge-shaped configuration that was adopted by all groups on January 13, 1943, and remained standard through September 1943. In 1943, the use of assembly ships, modified older bombers with unique paint schemes, to organize combat boxes was devised. These planes continued to be used throughout the war, even with the invention of other