vietnam tunnels
The tunnel systems were of great importance to the Viet Cong in their resistance to American forces, and played a major role in North Vietnam winning the war. The Cu Chi tunnels were built over a period of 25 years that began sometime in the late 1940s during the war against the French.
A group of university students have uncovered evidence that China may have many more nuclear weapons than previously thought. Capabilities: After translating secret military documents, forums and studying images of a network of tunnels in China, the students believe the country could have as many as 3,000 warheads.