As one of the Vietnam War's final battles raged four decades ago, Quynh Pham lay with her mother in a field covered in a stranger's blood. They survived only by pretending to be dead. 

They were among an exodus of over a million South Vietnamese who fled oppression and uncertainty before and after US forces retreated and victorious North Vietnamese tanks rolled into Saigon in April 1975, reuniting the two sides under communism. 

Pham, 41, resettled in California and is now owner of an art gallery in Ho Chi Minh City, one of a stream of Vietnamese Americans who found their fortunes in a fast-changing Vietnam where capitalism is thriving under communist rule. 

Pham runs leading art house Galerie Quynh. In the 17 years she's lived in Vietnam, her mother has refused to visit. 

"When I moved back to Vietnam, she disowned me," said Pham. "She said, 'You're not my daughter.'" 

They've since buried the hatchet, but Pham's mother has bitter memories and can't understand why she returned. 

The war drove boatloads of Vietnamese to the United States, which had more than 1.5 million citizens of Vietnamese origin in a 2010 census. Others resettled in Australia, Canada, Britain and France via refugee camps in Asia, surviving perilous voyages on crowded, rickety boats on which thousands starved or drowned.