the cost of armor protection thus led to a relatively unbalanced design. Tactical mobility While the M18 was capable of high road speeds, this attribute was difficult to use successfully in combat. Although sustained travel at high speeds was hardly ever used outside of the Allied response during the Battle of the Bulge, most Hellcat crews found the higher speeds especially useful in a sprint to flank German tanks, which had relatively slow turret traverse speeds, and such maneuvering allowed the tank destroyer crew to direct a shot into the enemy's thinner side or rear armor. The open top proved an advantage in terms of allowing the TD crews significantly better visibility than their opponents, many of which were German tank destroyers that did not have revolving turrets and were handicapped by poor lateral visibility. In general, Hellcat crews were complimentary of their vehicle's performance and capabilities but did complain that the open top created a cold interior in the Northern European winter of 1944–45. This problem was exacerbated because the air-cooled engine pulled some of its cooling air through the crew compartment, creating, in effect, a large armor-plated refrigerator; it proved impossible to seal off the crew compartment entirely from engine-induced drafts. Production Original plans called for a total of 8,986 M18s to be supplied: 1,600 for Lend-Lease to other countries and 7,386 for the U.S. Army. The production plans of the M18 were curtailed to 2,507 vehicles, including the six pilot models. The reasons behind the reduction (in no particular order) were: The 76mm gun was already inadequate for the thick and/or steeply sloped frontal armor of later German tanks and the Army Ground Forces (AGF) preferred to get the 90 mm Gun Motor Carriage M36 into service, despite Tank Destroyer Force commander Andrew Bruce's objections to adopting it The number of self-propelled tank destroyer battalions had been approximately halved due to a policy change forced by the AGF, who wanted towed guns to be used and hence far fewer self-propelled units were needed for the Tank Destroyers There was little potential Lend-Lease activity: Britain and the Soviet Union "had little interest". Two, listed as "T70", were transferred to the United Kingdom, and five to the Soviet Union. Production of M18 Hellcats ran from July 1943 until October 1944, with 2,507 built. In March 1944, the T70 was standardized by the Ordnance Department as the 76 mm Gun