apparent that anti-aircraft units had been over-produced. Many units were then broken up for infantry replacements. Armor While Army Ground Forces endeavored to provide the troops with the best equipment available, they were not always able to provide better equipment than the German enemy. This was particularly apparent with respect to armor. American commanders tended, when forced to make a choice, to prefer mobility to firepower. The result was a number of uninspiring designs. In particular, the M6 Heavy Tank was a dud which convinced Army Ground Forces that heavy tanks were no good and Ordnance Department that Army Ground Forces did not really want one. The M4 Sherman medium tank found itself out-performed by German tanks which began appearing in 1943. Opposition from Army Ground Forces was one of the primary factors for the late and limited introduction of the M26 Pershing into the European Theater. In 1942, the Operations Division (OPD) of the War Department General Staff estimated that, by the end of 1943, 140 divisions would be mobilized, of which 46 would be armored. A severe shortage of shipping space, combined with Army Ground Forces doubts about whether this was the correct ratio of infantry armored units, led to this being revised downward to just 16 armored divisions actually being active in 1943. Trimming the tables of organization of the armored divisions in 1943, Army Ground Forces cut the number of tank battalions in the armored division from 6 to 3 and reduced the number of tanks from 390 to 263. In process, the number of non-divisional tank battalions increased to 65, permitting more combined training with the infantry divisions. Later, it became standard practice to attach a non-divisional tank battalion to each infantry division where possible. Almost 4,000 personnel were cut from the division establishment although the number of Sherman tanks was only reduced by a quarter. While the old armored division organization was cumbersome and inefficient, the new was flexible but sometimes too lean and light, requiring supplementing. All armored divisions were converted to the new tables except the 2nd and 3rd, which remained under the old, with some modifications. Artillery Although also frequently out-ranged by their German counterparts, American artillery built up a reputation for effectiveness and the infantry increasingly relied on the artillery to get them forward. The War Department General Staff ignored the Army Ground Force's recommendations for a powerful heavy artillery