sentences:  Their attack was aided by tear gas, delivered either by sappers (using grenades) or mixed in with regular high-explosive mortar rounds as part of the bombardment.Nolan also documents the VC use of CS gas in his narrative of the attack.The attack against the B-TOC was made easier by Lt. Col. Doyle's failure to post armed guards at the bunker's entrances (which was a violation of brigade policy), preventing any early warning.