 While allied forces thus failed to search and destroy significant contingents of enemy forces, they did manage to uncover parts of the VC's complex tunnel system where large amounts of VC supplies and documents were found.In order to infiltrate these vast underground complexes, the US military used specifically trained teams (so-called "tunnel rats") for the first time in the war.After having been searched, tunnel complexes were destroyed using a combination of acetylene gas and conventional demolition charges.