This was particularly true of his 60 and 82mm mortars, which are easily displaced forward and shifted to alternate positions. These light mortars were difficult to locate by our observers mainly because of the small size and limited development of their positions, and the fact that they are moved frequently. A large number of enemy mortars were fired from bunkers deep in the ground with only a narrow aperture at the top through which to fire. There were some instances, during the Battle of Bunker Hill, when the enemy brought his 60mm mortars out from cover on the forward slope and set them up in the open near the crest of the ridge. After delivering several rounds, the mortars would then displace quickly back to a covered position. During August, mortar fire averaged between 50 and 60 percent of the total incoming received by the 1st Marine Division.[201] [201] 1stMarDiv ComdD, Aug 52, p. 2. Further information about the Chinese was also derived at this time, although not always directly associated with the battle. Deserters picked up in the left sectors of the 1st and 5th Marines on 12 and 13 August and papers taken from enemy dead on the 13th confirmed earlier-reported dispositions of Chinese units. One prisoner, from the artillery regiment of the 118th Division, the unit facing the major part of the 1st Marines line, indicated that another artillery regiment had been assigned to support his division. If true, this extra unit would account for both the increased Chinese fires in the Bunker area and the additional artillery emplacements that photo planes had spotted in the 118th Division sector. Infantry units of this division, the Marines observed, introduced no new techniques or equipment during the battle. Prior intelligence had provided the 1st Marines with typical enemy ground attack tactics. Neither the Chinese envelopment of Siberia, Stromboli, and Bunker nor the diversion against Hill 48A before the main attack on Hill 122 represented a departure from normal CCF practice. Nor was the earlier Marine diversion new, but unlike the Chinese attempt, the 1st Marines tactic was successful. Just before the maneuver, the division pulled off another strategem, described by General Selden in a letter to General Shepherd: I worked a ruse that morning which proved to be very profitable. Throughout the Eighth Army front, it had been routine to put on a strike, this to be followed by smoke, then a good artillery barrage, with troops following for the assault. This was done with the exception that there were no troops. The enemy, thinking that there were troops, opened up with everything. The only damage inflicted was on their own forces.... While they were firing on their own troops, we again opened fire with our artillery, just to help the situation along.[202] [202] MajGen John T. Selden ltr to Gen Lemuel C. Shepherd, Jr., dtd 14 Aug 52.