By the tens of thousands they immigrated 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.

Now, many former refugees and their offspring are reaping the gains of Vietnam's transition to an open market economy and middle-class growth, tapping a young consumer population that's wholeheartedly embracing Western culture.

One of the most notable is David Duong the founder of Oakland California based Waste Solutions, one of the most successful Vietnamese businessmen in the US.

Duong, whose father owned the largest recycling company and paper mill in South Vietnam, was born into wealth and lived in a seven-story mansion in Saigon. Following the fall of Saigon, David, then 15 fled with just the clothes on their backs.

The family eventually made it to the US where they landed in San Francisco’s Tenderloin District. David quickly learned the road to success wasn’t paved with gold, but with cardboard, as every day after school he would work until midnight collecting cardboard for recycle.

It was a job his family did every day for years. The payoff was their first recycling warehouse in West Oakland, which eventually led to California Waste Solutions a multi-million dollar company employing 300 people handling recycling in Oakland and San Jose California.

In 2006, Duong received a call from the Vietnam government, asking him to consider returning to Vietnam and building on his family’s roots. He accepted the offer and invested US$150 million in Vietnam Waste Solutions, which manages solid waste collection, landfills, recycling and composting.

On this 40th anniversary of the fall of Saigon, David Duong says he’s not bitter about what his family lost. Rather, he’s thankful for the ability to return, reinvest and help the communities he left.

Duong openly acknowledges there are many Vietnamese-Americans who refuse to do business with the Vietnam government. But he said for him, investing in Vietnam was just the right thing to do.

Then there is the case of Nguyen Van Cong, an engineer, who returned from France after immigrating there following the war’s end. Since his return, Cong has been instrumental in bringing know-how and capital related to the construction of seven 20 storey-buildings in HCM City.

Most notably he played a pivotal role in constructing the Ham Nghi Tower, Sunwah Tower and Saigon Centre. Cong and a group of OV engineers from France also spent considerable time assisting smaller communities in the south implement badly needed state of the art infrastructure projects.

Using their personal funds, the group has played an important part in replacing nearly 200 outdated bamboo bridges with modernized concrete and steel bridges in the Mekong Delta and the south-eastern region.

They currently have plans to expand their assistance and fabricate and erect more bridges in the northern provinces of the nation this year.

 “I will continue to help people in my homeland,” Cong said. “I travel a lot and see that this is very important. Local residents are very happy when a safe and solid bridge has been constructed.”

Meanwhile, a large number of OVs from Thailand have returned home at the behest of late President Ho Chi Minh since 1960 and have made vitally important contributions to the nation’s socio-economic development.

Phan Thi Huong, who returned from Thailand 20 years ago, is now the Director of the Van Minh AB Company specializing in producing and developing recirculating aquaculture systems.

She was born in an OVs family with three generations residing in Thailand.

She has always educated her children to appreciate the homeland. Apart from businesses activities, she has actively served as bridge to help OVs learn more about new governmental policies and reared them to faithfully contribute to national construction.

Ms Huong said future generations should strive to impart patriotism to young OVs and help them understand Vietnam’s culture and traditions to instil in them a strong sense of national pride and achievement.

Though their role is often overlooked, OVs have been a boon for Vietnam's economy. Remittances are expected to reach US$13-14 billion this year, central bank data shows, compared with US$12 billion in 2014.

These remittances remain a key part of the country's economy, providing a much needed influx of foreign currency equivalent to about 8% of the nation’s gross domestic product. More than half of the capital comes from the US.

VOV