It was January 30, 1968, three years after President Lyndon B. Johnson had ordered 125,000 American troops to Vietnam to ward off a communist takeover of the south, and the rest of Southeast Asia.

HANOI, Vietnam — Ngoc Dai, a 23-year-old soldier in the People’s Army of Vietnam, was fighting the Americans near the besieged Khe Sanh combat base when his unit received elating orders. They were to ...

China, Vietnam, the Philippines, Taiwan, Malaysia and Brunei all have territorial claims in the South China Sea, which include islands and other strategic maritime features.