Such propaganda opportunities may have been purchased by significant manpower losses on the part of the ground troops of the PLA. Without effective air support the troops of the PLA suffered heavy casualties, estimated to be from 20,000 to 40,000 men. At one time during the campaign there may have been as many as 250,000 PLA troops (about 21 infantry divisions from 8 army corps—the 41st, 54th, 42d, 43rd, and 55th of the Kwangsi Command, as well as the 11th, 14th, and 13th of the Yunnan Command) engaged in the fighting. Without air support to suppress enemy fire and neutralize strongpoints, the ground forces of the PLA were compelled to absorb the full impact of the enemy’s firepower. Chinese Communist ground control apparently ordered the air units of the PLAAF not to engage any enemy aircraft (generally the technologically sophisticated MiG-21s and possibly the MiG-23 of the air force of the SRV) or attack ground positions which were defended by tough SAM defense systems supporting the Vietnamese army.12 There is more than a suggestion that the Chinese Communist command had little confidence in the effectiveness of the air-to-air ordnance available to PLAAF combat pilots, so rather than lose expensive major military equipment and trained pilots (in very short supply from the lapse in pilot training that occurred during the Great Proletarian Cultural Revolution) the aircraft of the Chinese Communist air force were just not committed to combat.