Along the base perimeter, most of the troops took cover in their conex bunkers when the mortar barrage began. This allowed the sappers to close rapidly without any danger of return fire, and in many cases they were through the lines before the defenders moved from their bunkers to the sandbagged trench line. The first man to report seeing the sappers had been sleeping on top of his bunker, but didn't spot them until they were "two-thirds of the way to the trench that connected the bunkers." Many of 1/46th Infantry's casualties occurred during this period and were concentrated among those units along the gently sloping side of the base. Charlie Company's First Platoon, occupying Bunkers 15-19 along the side of the perimeter that had a steep slope, was relatively untouched by the initial assault and manned their positions in the trench line. By contrast, Second Platoon in the southern sector had ten men killed and eleven wounded before Col Doyle and Capt Spilberg moved toward the Charlie Company CP.