Under its announced no-first-use doctrine, the Chinese government says it would launch a retaliatory nuclear attack only after it survived a nuclear strike. To assure the survival of an adequate number of weapons for retaliation, China has just two primary options: One is to build more warheads and launchers. But to survive a US preemptive attack that could involve as many as 1,000 warheads and extremely accurate targeting, China would need a huge nuclear arsenal. So rather than greatly expand its arsenal, China has chosen the second option: It has protected its small missile force by moving it underground.