Unless you knew modern Chinese history well, you probably have no idea what I am talking about. Most people only knew that "after Chiang Kai-Shek's Nationalists, or KMT, was defeated by Mao Tse-tung Communists, Chiang took his army to Taiwan and settled there and turned it into an economic powerhouse..." What most people do not know is that a portion of the KMT Eight Army, under General Li Mi, comprised of KMT 26th and 93rd Divisions, actually remained in Yunnan after after Chiang's retreat, and in order to grow their support, they, with permission from Chiang, allied themselves with the the Karen National Defense Organization and tried to help them take over Myanmar / Burma. Those of you who watched Rambo (2008) may recognize "Karen", as in the Karen Rebels. Yes, it's the same people, still fighting the Myanmar government decades later. And there are a lot more involvement of the Lost Army...

The Lost Army ended up splitting up when Burmese forces attacked them and some waged guerilla war alongside the Karen people against Burmese forces for a while, while others, esp. those with their dependents and families, fled to Laos and Thailand. As the force size shrank, they became known as the "Lost Battalion" instead. And to sustain themselves, they took up growing poppy plants, essentially creating the Golden Triangle, the source of the opium and heroin supply for decades to come. The Lost Battalion started getting covert US support to keep the Chinese Communists bottled up in China, but when Burmese government allied themselves with Beijing and both forces converged on the frontiers to squeeze out the KMT remnants (and repeated attempts by the KMT forces failed to gain permanent foothold in Yunnan), plus a diplomatic protest by Burmese government to the UN alleging that KMT was trying to overthrow them, Chiang was forced to issue an order to General Li Mi that he's to retreat to Taiwan with as much force he can convince to come along. What's not well known at the time was the Thai government was also recruiting the KMT force, as Thai was concerned about their northern border with China and Burma, and they are afraid China may intend to infiltrate the frontier and incite rebellion there. So it was to Thai advantage that they keep the KMT forces in that region as a buffer. All that changed in the 1970s as US withdrew from Vietnam, and started pushing Burma and Thailand to suppress the opium trade. As a result, Thai offered many KMT soldiers, whom by then, became the primary racketeers of the opium trade in the area, residency in Thailand if they are willing to give up their opium trade / racketeering operation. And many did. The rest fled to Burma, and came under attack by Burmese forces also under pressure by the US to terminate the opium trade. However, life of the old soldiers in Thailand was not ideal, as the Thai do NOT want them to create a state within a state, and thus, they were resettled in smaller groups all over Southern Thailand, and prohibited from operating Chinese schools, as a part of assimilation policy. However, some villages in the Golden Triangle refused to be assimilated, and even today, speaks Chinese, and hangs ROC flags all over. And there are dozens of villages along the border of Myanmar and Thailand just like this. What may be surprising is thousands of KMT soldiers, who decided to stay in China, were discriminated against by the Chinese government. For decades, they were not recognized as war veterans, an "honor" reserved for those who fought for Mao. However, a change of heart by the Chinese government in 2013 actually allowed those few KMT soldiers still surviving in China, then in their nineties, to receive welfare benefits.