To clear them, the U.S., Australian, and New Zealander armies used —small-framed volunteers who went where no one else would.
If you ever find a file like Tunnel.Rats.rar in your own digital travels, remember the men it represents. They were a "rare breed," as some veteran communities describe them—the bravest of the brave who did a job that most people couldn't even imagine in their worst nightmares.
During the Vietnam War, the Viet Cong created an incredibly complex web of underground tunnels (most famously the Tunnels of Cu Chi ). These weren't just hideouts; they were entire cities with hospitals, kitchens, and weapon caches.