Vietnam stayed on Earth. At the time it seemed like a truly insane path to take for a tropical nation facing both the Deluge and a nuclear winter, but to those in power it was the only option. Despite colonization successes decades earlier in cooperation with the Arabic sphere, Vietnam's massive state-owned salvation arks were far from ready due to years of unchecked bureaucratic corruption in the Office of Colonization, and there were few contingencies in place to deal with widespread capitalist greed and incompetence. The government's final decision was in large part due to the work of the Ministry of Planning and Investment's Joint Disaster Research Committee, which stood fast by its prediction that within a hundred years Earth's atmosphere would be breathable again- if never again pure. Many Viets who could afford to leave did, by the millions, aboard foreign arks or private spacecraft, depending on how long they'd spent bleeding the country dry. Those who did come back (most did, eventually) were not welcomed with open arms but instead made to face their reckoning by a nation broken and hardened in the Fall.
In retrospect, though the JDRC's report was directly responsible for the short-term extinction of the vast majority of the rural Vietnamese population, in the end its decision preserved the Vietnamese people from the fate that befell the nations that left their mother planet. To the shock of most world leaders and the billions of refugees they'd launched into the unknown, space and the extraterrestrial planets proved to be just as inhospitable to human life as post-apocalyptic earth was. Mankind had vastly overestimated its own adaptability and, more importantly, its terraforming abilities. Wars in space turned out to be not so different from the ones that had just finished on Earth; one by one nations perished lobbing designer viruses and giant rocks at each other over inaccessible mineral deposits lodged in frozen rocks strewn across the solar system. A few of the Great Powers barely survived, some through their vast material wealth, and others through their abundance of human resources. In the end, nobody won... except Vietnam.
While the Americans and Germans and Russians and Chinese were busy killing each other above, on Earth the resurrected State Planning Commission of Vietnam was busy building. Today, the Republic of Vietnam (which dropped the 'Socialist' from its name in 2099) is the most populous sovereign human nation on Earth- and possibly in the entire solar system, if one does not consider the cyborg monstrosities the Nigerians and their satellites have become humans- with a stable population of 140 million citizens: 65 million of which live in the Saigon Arcological Reclamation Community, one of two designated "Human preservation municipalities" in the Republic. The SARC is also the temporary home of the Sovereign Organization of the United States of America (SOUSA)- not affiliated in any way with the lunar-based United States of America- while it is pursuing negotiations with Vietnamese government for the eventual reclamation of the North American continent.
