Củ Chi tunnels
The Củ Chi tunnels were the location of several military campaigns during the Vietnam War , and were the Viet Cong's base of operations for the Tết Offensive in 1968 . 
<triplet> Vietnam War <subj> Viet Cong <obj> participant <triplet> Viet Cong <subj> Vietnam War <obj> conflict <triplet> Tết Offensive <subj> Vietnam War <obj> part of <subj> Viet Cong <obj> participant