Pham Van Thinh can see the back of an LG electronics factory from his patio, and in his eyes, nothing is more beautiful than that bright white behemoth.

Some nights, when workers stream out after 8 p.m., their lanyards flashing ID cards with new-hire faces, he walks amid the crowd, soaking up the energy of a once-poor village near Vietnam’s northern port of Haiphong that has suddenly joined the march of global trade.

“It makes me happy,” said Mr. Van Thinh, 73, a retired police chief who fought for the Communist north in the Vietnam War. “All these young people, they have better lives.”

Six years ago, this cluster of prosperity did not exist. Then President Donald J. Trump hit China with tariffs, igniting a global search for alternatives to Chinese manufacturing.

Few nations, if any, have benefited more than Vietnam from the scramble that followed — especially north Vietnam, historically an economic laggard compared to the more cosmopolitan south. Around Haiphong, a few hours’ drive from China, factories bloomed. The LG plant expanded exponentially; the industrial park nearby filled up with Chinese companies adding production abroad. Rural hamlets like Mr. Van Thinh’s — once known for little more than rice fields and dreams — grew almost overnight into boom towns of 30,000.