Just before its OPLR was withdrawn in favor of an observation line, the 1st Korean Regiment was struck by the Chinese in the area immediately north of the 1–2 April clash. Beginning at 0100 on 17 April, the enemy placed a 15-minute preparatory fire on the left flank of the 3d Battalion, occupying the regimental right sector. The CCF then probed friendly lines in and around the area pounded during the preliminary fires. Three separate attacks took place before 0400, when the Communists withdrew. In these probes, the Chinese made free use of automatic weapons; the enemy’s well-coordinated action attested to their training and discipline. Confirmed casualties were 36 CCF and 2 Koreans killed. The KMCs suffered 5 wounded and estimated that 70 Chinese had been wounded. Although the South Koreans frequently called down artillery support during the attack, most of the casualties inflicted on the enemy were from rifle and machine gun fire. The 17 April probe was to mark the last major infantry action for the 1st Marine Division during its second month on JAMESTOWN. Throughout the month a total of 5,000 rounds of artillery fire and 3,786 rounds of mortar fire fell in the division sector. On 2 April the greatest volume for any single day was received: 3,000 artillery and 118 mortar rounds. An average day’s incoming, during April, was approximately 167 artillery and 125 mortar rounds. _Strengthening the Line_[49] [49] Unless otherwise noted, the material in this section is derived from: _PacFlt EvalRpt_ No. 4, Chap. 9; 1stMarDiv ComdD, Apr 52; KMC Regt UnitRpt 46, dtd 17 Apr 52. Even before the Communists had launched their mid-April attacks against JAMESTOWN, the 1st Marine Division had implemented plans to strengthen its line in western Korea. Besides the digging, timbering, and sandbagging to accomplish a major improvement of the physical defenses, General Selden required Marine infantry regiments to conduct an aggressive defense of their sector of responsibility. He ordered MLR units to employ snipers all along JAMESTOWN and to dispatch daily patrols forward of the line to ambush, raid, kill, or capture Chinese and their positions. The division commander further directed that supporting arms such as artillery, tank, and air, when available, be used to destroy hostile defenses, harass the enemy, and break up his assemblies as well as to protect Marine positions.