As friction increases between China and Vietnam over the South China Sea, an important question is how Vietnam’s military, famed decades ago for its resilience and guerrilla warfare, measures up. For the last two months, Chinese and Vietnamese Coast Guard vessels have been jostling each other around a billion-dollar Chinese oil rig that Vietnam says was unilaterally placed in its waters by Beijing. (Beijing says the waters are Chinese.) Warships from both countries lurk in the distance, and from time to time, the Chinese send air force fighters into the rig’s vicinity to show they mean business. Prof. Lyle J. Goldstein, associate professor at the China Maritime Studies Institute at the Naval War College in Rhode Island, is well qualified to examine the capacities of the Chinese and Vietnamese militaries. The two armies worked together in Vietnam to topple the French in the 1950s, and to defeat the Americans in the Vietnam War. In 1979, the Chinese invaded Vietnam — to teach its neigh