There is no doubt that when Indonesian troops invaded East Timor in December 1975, it was a deliberate decision taken at the highest levels of the Indonesian government and personally approved by President Suharto. The question remains, why did he do it?

Suharto was notoriously inscrutable, capable of hiding his true thoughts from all around him. He was also highly skilled at playing different factions off against each other. Aloof and impenetrable, his true motives were never easy to discern. However, it is possible to isolate a number of reasons why Indonesia might have chosen to annexe East Timor. Here are the main ones:

1. Oil. Indonesia was blessed with massive reserves of oil, and there was good reason within the geological community to suppose similar reserves lay under the Timor Sea. Incorporating East Timor into Mother Indonesia would give the country control of these potential reserves and access to the wealth they promised.

Having said that, Indonesia had never made any territorial claims on East Timor, and certainly not while Portugal was in control. Whilst Suharto was a tough dictator, he was no Saddam Hussein, and didn’t have a history of aggressive expansionism. He was also sensitive to his reputation in the West and was scrupulous about ensuring he would not upset the United States before embarking upon any foreign policy adventure. Besides, he had enough on his hands controlling the 3,000 or so islands that made up Indonesia without taking on additional troublesome commitments. Indonesia was already mineral rich, Suharto’s problems lay elsewhere.

2. Fear of Communism. Suharto loathed communism, and presided over the 1965 bloodbath that effectively extinguished communism as a political force in the country. The idea of a socialist state setting itself up on his doorstep would have been anathema to him; taking decisive action to crush it would have been a fairly easy sell to the Americans, still reeling from defeats in Vietnam and Cambodia.

3. Opportunism. The collapse of the Salazar regime in Lisbon created a power vacuum in East Timor, and although the socialist leaning Fretilin attempted to fill it, they were no match for the economic or military might of Indonesia. Neither was Portugal, despite their protests, in a position to do anything. With the covert blessing of the United States and the reluctance of Australia to stand up to Indonesia, Suharto could be excused for seeing East Timor as a gift handed to him on a plate. All he had to do was turn up and march in.

No doubt each of these factors played a part in Indonesia’s decision to go ahead and take East Timor for themselves. What is harder to ascertain is the relative importance each factor had in the equation. To do that one would have to get an insight into the workings of Suharto’s mind, something few, if any, individuals ever came close to achieving.