The trauma of the "Jap camps" in the Dutch East Indies, as they are still often called today, has been an important part of the Dutch experience. For a long time after WWII, there were many Dutch people who had either been detained in such a camp themselves or whose relatives had been in one. However, curiously enough, I've never heard why the Japanese felt the need to imprison civilians on such a large scale. Recently I visited Bronbeek, a museum dedicated to the history of the Dutch East Indies with a particular focus on WWII and the Indonesian war of independence that followed – but even there, the Japanese were treated more or less like a force of nature, their motives, command structure, and internal disagreements abstracted away.
So... why did they do it? Was it an attempt to court sympathy among the native population (which I'm vaguely aware the Japanese tried in other ways), by showing that their colonial oppressors were finally getting their just desserts? A pre-emptive measure against a group considered likely to resist the occupation? A way to uproot the old power structure as rigorously as possible? Or something else entirely?
More generally, good sources about the Japanese perspective on World War II in the Dutch East Indies would be welcome. Unlike the Germans, the Japanese are still very much treated as one-dimensional "cartoon villains" in the Dutch popular historiography of WWII, and I'd love to get a more detailed picture.
/u/midnightrambulador
Great question, unfortunately this is rather under-studied. But one book I know of that is of interest to you: Shigeru Sato's War, Nationalism and Peasants: Java Under the Japanese Occupation 1942-45. I do not know how much you know of the situation in the crucial year 1942, so let me summarize a few facts that are not well-known, and iirc Bronbeek does not explain well.
In 1941-2, as the Netherlands fall under German occupation, the Japanese asked them to command the administration of the DEI to send war materiel to Japan. This was in expectation that the DEI administrators would behave similarly to the those in French Indochina, who collaborated with the Japanese. However, DEI administrators instead followed the line drawn by Shell and Stanvac, major oil companies in the region, who at this point were directed by the US. Thus, the DEI instead effectively continued their policy to boycott Japan.
When Japan finally invaded the DEI, they had expected a slow and steady transition as they would fight their way into total control. However, the DEI collapsed much more quickly than they expected: in 9 days instead of in 3 months. Defense of the DEI relied on UK and US leadership, which vanished as the Japanese advanced. So the Japanese were under-prepared for transition.
Prior to surrender, DEI military command had encouraged Dutch civilian workers in the DEI to remain at their posts, for the sake of the people of the DEI, with the expectation that the Japanese would treat them similarly as the Japanese did French civilian workers in French Indochina. Thus, in many places Dutch civilian workers gave the surrender as the DEI miilitary had retreated, in order to minimize damage to facilities and towns.
And most importantly,
To quote The Emergence of a National Economy: an economic history of Indonesia, 1800-2000:
The causes of economic decline were structural and institutional. Physical damage was not the main problem, because Japanese bombing had been confined to military targets and last-minute Dutch sabotage was neither systematic nor effective. Rather, the colonial economy was like a sophisticated machine suddenly driven hard by an untrained crew.
Thus, the Japanese turned a largely self-sufficient economy into poverty and starvation, and of course the Dutch civilians in camps suffered tremendously as did everybody else.
Hope the above helps.