What underground nuclear bunker near Blue Ridge Summit, Pennsylvania known as "underground Pentagon" became operational in 1966?
Deep Underground Command Center The Deep Underground Command Center (DUCC) was a United States military installation that was proposed on January 31, 1962 , to be "a very deep underground center close to the Pentagon, perhaps 3,000-4,000 feet down, protected to withstand direct hits by high-yield weapons and endure about 30 days in a post-attack period" . The DUCC would have been built as "an austere 50-man … or an expanded 300-man version (with the former built to permit expansion into the latter, if desired)" . It was designed to withstand multiple direct hits of 200 to 300 Megaton weapons bursting at the surface or 100 MT weapons penetrating to depths of 70-100 feet. Based on Strategic Air Command's Deep Underground "Support" Center (DUSC) planned near the Cheyenne Mountain nuclear bunker , the DUCC plan was recommended to President John F. Kennedy for fiscal year 1965 funding shortly before his assassination , but the underground DUCC, SAC's DUSC, and NORAD's Super Combat Centers were never built. Other contemporary underground installations did see upgrades, such as the 1953 Site R which was "hardened further to about 140 psi blast resistance by 1963" , or completion, such as the NORAD's Canadian bunker in 1963, and NORAD's Combat Operations Center & Space Defense Center in the Cheyenne Mountain bunker became operational in 1966.
Underground Great Wall of China The Underground Great Wall of China is the informal name for the vast system of underground tunnels China uses to store and transport mobile intercontinental ballistic missiles. Due to the immense amount of secrecy surrounding the tunnels, not much information about them is publicly available however it is believed that the tunnels allow for mobile ICBMs to be shuttled around to different silos and/or stored in reinforced underground bunkers. This greatly enhances the ICBMs chance of survival in a direct nuclear strike, which enables their use in a second strike unlike ICBMs based in static nuclear silos which generally do not survive a direct nuclear attack.