 On 29 January a Marine observer at Con Thien using a Starlight Scope spotted a PAVN convoy moving about 1 km north of the Ben Hai River and called in artillery air strikes.The PAVN responded by launching five SAM-2 missiles on the attacking aircraft, which proceeded to destroy both the convoy and the SAM site.By the end of January the defensive positions on the trace line, including C-2, C-2A and Con Thien (A-4), were largely complete, although there was abundant evidence of continued PAVN infiltration across the DMZ.