Immediately after taking command, Peers instituted guidelines for his units in order to prevent them from being isolated and overrun in the rugged terrain, which also did much to negate the U.S. superiority in firepower. Battalions were to act as single units instead of breaking down into individual companies in order to search for their enemy. If rifle companies had to act independently, they were not to operate more than one kilometer or one hour's march from one another. If contact with the enemy was made, the unit was to be immediately reinforced. These measures went far in reducing the 4th Infantry's casualties. These heavy enemy contacts prompted Peers to request reinforcement, and as a result, on 17 June, two battalions of Brigadier General John R. Deane's 173rd Airborne Brigade were moved into the Đắk Tô area to begin sweeping the jungle-covered mountains in Operation Greeley. The 173rd had been operating near Bien Hoa Air Base outside Saigon and had been in combat only against VC guerrillas. Prior to its deployment to the highlands, Peer's operations officer, Colonel William J. Livsey, attempted to warn the Airborne officers of the hazards of campaigning in the Highlands. He also advised them that PAVN regulars were a much better equipped and motivated force than the VC. These warnings, however, made little impression on the paratroopers, who were unaccustomed to PAVN tactics and strength in the area. On 20 June, Company C, 2nd Battalion, 503rd Infantry Regiment discovered the bodies of a CIDG unit that had been missing for four days on Hill 1338 (), the dominant hill mass south of Dak To. Supported by Company A, the Americans moved up the hill and set up for the night. At 06:58 the following morning, Company A began moving alone up a ridge finger and triggered an ambush by the PAVN 6th Battalion, 24th Regiment. Company C was ordered to go to support, but heavy vegetation and difficult terrain made movement extremely difficult. Artillery support was rendered ineffective by the limited range of visibility and the "belt-grabbing" - or "hugging" - tactics of the PAVN (PAVN/VC troops were instructed to open their actions or move as close to American forces as possible, thereby negating U.S. artillery, aerial, and helicopter gunship strikes, which demanded a safety margin for utilization – hence, "grabbing the enemy by the belt).