China is building its military forces faster than U.S. intelligence and military analysts expected, prompting fears that Beijing will attack Taiwan in the next two years, according to Pentagon officials. U.S. defense and intelligence officials say all the signs point in one troubling direction: Beijing then will be forced to go to war with the United States, which has vowed to defend Taiwan against a Chinese attack. China's military buildup includes an array of new high-technology weapons, such as warships, submarines, missiles and a maneuverable warhead designed to defeat U.S. missile defenses. Recent intelligence reports also show that China has...