Nothing happens in a vacuum. Every event in history has a lead-in and an aftermath.
The story of the romusha of WW2 is no different. Hundreds of thousands of Tamil coolies were available to be victimized as workers for the Japanese Army because they found themselves in dire straits after the IJA overran Malaya. The ancestors of these people had been imported to Malaya generations before to work the rubber and sugar cane plantations. They lived in a highly structured and socialized system under the auspices of their British overlords. They were little more than slaves. Most were still illiterate. They were never allowed to integrate into Malaya society. Few even spoke the local language. They were isolated into their own world within a world.
In 1942, all of this collapsed as the IJA swept across Malaya. The British fled; the plantations closed. The Tamils were abandoned. But the Japanese were offering the Greater Asian Co-prosperity Sphere:
[ https://en.wikipedia.org/wiki/Greater_East_Asia_Co-Prosperity_Sphere ] IOW, the Japanese were their saviors who would help them get out from under the boot of the British. All they had to do was to agree to go to work for the IJA at the incredible rate equivalent to 1US$ per day! These abandoned starving people were being offered a lifeline and they jumped at the chance. Whole families packed up their meager belongings and boarded trains that they thought were going to northern Malaya, but they didn’t stop there. They crossed into Thailand and continued north to a place called BanPong.
There the cargo – they could hardly be called passengers – were pushed out of the boogies and into a squalid reception or transit camp. To say the least, these people were confused. After a short stop, a little food and rest, they were told to start walking west. They had no idea where they were, where they were going nor how long it would take to get there. Food, shelter and necessities much less amenities were nonexistent. It became readily apparent that they had traded down from their lives as coolies under the British. Communication between them and their controllers was nearly impossible. They were to be the tools that the IJA Engineers would use to build a railway. Tools that, when broken, would simply be discarded.
There were also thousands of Allied POWs who were caught up in this same web of deceit. But at least they had the military organization and disciple to fall back on. There were also translators available. If life for them was bad, it was infinitely worst for the romusha. Interspersed among the Tamils were peoples of other nationalities and ethnic groups, but the Japanese usually kept each group isolated from the others.
The earliest arrivals had a shorter trek to their assigned place of work. But the minimum was over 100 Kms. Many had to travel 3 times that far. Those who arrived in the spring of 1943 had the worst experiences of all the others. Not only was it monsoon season, but the Engineers had instituted the Speedo period of increased demand for work output; more work over longer hours. For many who arrived in the camps near the Burmese border, camp life was already a nightmare with inadequate shelter and food. Then cholera struck! In just a few weeks thousands died. After a 300Km trek, many of these workers hardly contributed anything to the building effort. They arrived sick and debilitated and died soon thereafter.
As a group, there is no record of their existence. No count of how many; no lists of names. Unlike for the POWs, no one recorded their deaths or place of burial. Many were never actually buried. In some cases, POWs were sent to nearby camps to build huge funeral pyres, especially if cholera was present in that camp.
Once the construction of the Thai-Burma Railway was completed in Oct 1943, most of the romusha and POWs were moved to ‘rest camps’ near the walled city of Kanchanaburi. POWs and romusha went to separate places. But, for the romusha, life in these camps was hardly better than in the jungle. They continued to die from the maladies they had contracted. The cholera outbreak was short-lived but malaria and dysentery as well as the multiple effects of malnutrition continued to claim lives.
Given that there were three different projects that the romusha were involved in in two different countries, there may have been as many as 500,000 of them. It is estimated that 40% of them died.
Even the end of the war did not bring relief. The various governments rushed to bring their soldiers home. No one helped the romusha. Although most of them were British subjects if not technically British citizens, London did nothing to get them back to their home! Well into 1947, many remained in Thailand. Some chose to settle there. Others began the months-long trek back to Malaya or Singapore. A few travelled by train; most walked.
Those who survived the return trip found themselves in a world very different from the pre-war plantations. The Greater Asian Co-prosperity Sphere had not exactly delivered what it had promised.