Except on the 11th, most of the tank firing in the fight for Bunker Hill through 14 August was accomplished during the hours of darkness. On the latter date, the cannons and machine guns of the mediums blasted directly at Chinese outposts opposite Colonel Layer’s regiment. The number of rounds that day fell off considerably from the high on the 13th; on the 15th the tanks in the 1st Marines area did not fire at all. Heavy rain that had accompanied the late afternoon thundershower that day made movement forward to firing positions impractical. By the next day, however, the ground was solid enough to permit some maneuvering by the tracked vehicles. They fired 52 rounds of 90mm shells and 14,750 machine gun rounds at automatic weapons positions and bunkers on the western slope of Hill 122. This marked the final tank mission in support of the 1st Marines in the battle for Bunker Hill. During the early part of the August fighting, tanks of the division were able to get the first real test of a technique of night support,[195] and at the same time experiment with a towing device to permit retrieval of disabled vehicles under fire without getting outside the tank. The use of the lights to support both the diversionary force and the defense of Hill 122 showed the value of these instruments. Lieutenant Colonel Williamson recommended that tanks be employed in pairs, one to spot and adjust fire and the other to fire. With respect to the towing device, he considered the new piece of equipment an improvement over the manual hook-up method, but noted that the device limited tank maneuverability and had a tendency when bouncing up and down over rough terrain to dig into the ground, impeding the forward progress of the vehicle. [195] The use of fighting lights to illuminate targets for tank gunners had been undertaken in July, but the results were inconclusive, owing to failure of one of the bulbs of the two lights tested. 1st TkBn ComdD, Aug 52, App. VI, Encl. 2. Declared the G-3, 1stMarDiv: “The diversion on Siberia was 100 percent effective, due largely to the new tank battle lights which we were using for the first time.” _Honsowetz ltr II._ _In Retrospect_[196] [196] Unless otherwise noted, the material in this section is derived from: FMFPac, _1stMarDiv Sum, Jul-Oct 52_; _PacFlt EvalRpt_ No. 5, Chaps. 8, 9; 1stMarDiv, 1stMar ComdDs, Aug 52.