The Pentagon visit by Gen. Cao Gangchuan was the first by a Chinese defense minister during the Bush administration, though Rumsfeld last year met with Chinese president Hu Jintao while Hu was vice president. The military leaders talked about the threat from North Korea's nuclear program, the global war on terrorism and prospects for future U.S.-Chinese military relations, defense officials said. The state of military-to-military ties between the two countries has been up and down for decades. Ties were severed after China's army-led crackdown in 1989 on student protests at Tiananmen Square. A 1994 visit to Beijing by then-Defense Secretary...