At the time, the state-of-the-art means for clearing a cave was to tie a rope around the waist of an infantryman, who would crawl in and toss ahead a grappling hook to probe for mines or booby traps.
U.S. commanders considered buried bombs and other booby-traps to be the biggest danger to the assault force, and they predicted the belt of land mines on the outskirts of town would be the biggest ever breached by North Atlantic Treaty Organization troops.