What is chiefly responsible for maintaining national unity in Indonesia?

a government that represses dissent

Explanation:

Indonesia is a country that has hundreds of different ethnic groups in its borders. Apart from different ethnic groups, the country also has numerous religious groups, though the Islam is by far the most dominant one. In order to be able to keep things in control and avoid rebellions and conflicts, the governments have been suing force, and is repressing dissent. People that try to oppose the government views and politics are marginalized, demonized, put in jails, or even end up dead, which can be seen very easily in the most recently occupied territories on New Guinea and Timor. It is a way that works, but it is also a way that breaks most of the international laws for human rights.