[Someone]

> Carpet bombing. You don’t get to bury things in the sand, much less unbury them.

https://en.wikipedia.org/wiki/Củ_Chi_tunnels#U.S._campaigns_...:

“Operation Crimp began on January 7, 1966, with B-52 bombers dropping 30-ton loads of high explosive onto the region of Củ Chi, effectively turning the once lush jungle into a pockmarked moonscape. Eight thousand troops from the U.S. 1st Infantry Division, 173rd Airborne Brigade Combat Team (including an artillery battery of the Royal Regiment of New Zealand Artillery), and the 1st Battalion, Royal Australian Regiment combed the region looking for any clues of PLAF activity.

The operation did not bring about the desired success. […]

By 1969, B-52s were freed from bombing North Vietnam and started "carpet bombing" Củ Chi and the rest of the Iron Triangle. Towards the end of the war, some of the tunnels were so heavily bombed that some portions actually caved in, and other sections were exposed. But the bombings were not able to destroy most parts of those tunnels.”