In April 1965, Harold Brown, at that time director of the Department of Defense Research and Engineering, stated the favored position was to consider the F-5 and begin studies of an "F-X". These early studies envisioned a production run of 800 to 1,000 aircraft and stressed maneuverability over speed; it also stated that the aircraft would not be considered without some level of ground-attack capability. On 1 August, Gabriel Disosway took command of Tactical Air Command and reiterated calls for the F-X, but lowered the required performance from Mach 3.0 to 2.5 to lower costs.