America's most advanced nuclear submarine was slicing through the water off Hawaii last month, 400 feet under the surface, when a sonar operator suddenly detected an ominous noise on his headphones.
It was a faint thump … thump … thump — the distinctive sound of a spinning, seven-bladed propeller on a Chinese attack submarine called a Shang by the Pentagon and its allies.
A neon green stripe on his sonar screen indicated that the Shang was only a few thousand yards off the U.S. sub's bow.
"Sonar contact!" he yelled to 15 officers and crew in the dimly lighted control room. "All stations, analyze!"
Within seconds, the...