After his first look inside the nerve center of the U.S. missile defense system, Defense Secretary Donald H. Rumsfeld on Sunday sounded a note of caution about expectations that interceptors poised in 10 underground silos here would work in the event of a missile attack by North Korea. Asked at a news conference whether he believed the missile shield was ready for use against a North Korean missile like the one test-fired unsuccessfully on July 4, Rumsfeld said he would not be fully convinced until the multibillion-dollar defense system has undergone more complete and realistic testing. Full Story