 On 27 October , an ARVN battalion at Sông Bé , the capital of Phước Long Province , came under attack by an entire North Vietnamese regiment . Two days later , another North Vietnamese Regiment attacked a U.S. Special Forces border outpost at Lộc Ninh , in Bình Long Province . This attack sparked a ten @-@ day battle that drew in elements of the U.S. 1st Infantry Division and the ARVN 18th Division and left 800 North Vietnamese troops dead at its conclusion . 
