up of bombers of one squadron, also in vees of three, with one additional bomber flying in the slot of the center rear (sixth position) of each squadron box, and known as "Tail-end Charlie". This seventh position was usually flown by the least experienced crew in the squadron and was vulnerable to fighter attack, so perilous that it was commonly called the "coffin corner" or "Purple Heart corner". The second unit of the group formation was configured identically, except that its boxes were named Dog, Easy, and Fox. Each position within a box was numbered, so that the group leader flew the Able One position while the Tail-end Charlie of the leftmost rear squadron flew Fox Seven. The second unit flew at an altitude approximately lower than the first unit. Because it was laterally wide, the six-box formation was not a compact formation, was cumbersome to fly, and thus was less efficient in bombing accuracy. The Fifteenth Air Force adopted the diamond formation during the summer of 1944 to increase its bombing accuracy, but this also had the negative consequences of increasing losses to flak. This formation reduced the number of boxes from six to four, each flying three elements of three planes each with a Tail-end Charlie. As with the six-box formation, the trailing elements were stacked downward from the high leader, and the Tail-end Charlie of the fourth box (Dog Ten) was still often referred to as "the Purple Heart position". The four-box formation proved easier to assemble and organize, provided a tight bomb pattern, and concentrated defensive firepower against fighter attacks. References Notes Bibliography Bowman, Martin W. (1997). USAAF Handbook 1939-1945, Stackpole Books, Capps, Robert S. (1997). Flying Colt: Liberator Pilot in Italy, Manor House, Freeman, Roger A. (1991). The Mighty Eighth War Manual, Motorbooks International, Morrison, Wilbur H. (1962), The Incredible 305th: The "Can Do" Bombers of World War II, Jove Books, Thompson, Robert L. (1995). Flying in Coffin Corner'', Whitewing Press, 398th Bomb Group Combat Formations Tactical formations World War II strategic bombing Aerial warfare tactics Military doctrines