From the Central Intelligence Agency (CIA), The World Factbook, Indonesia, Introduction, Background:

“The Portuguese conquered parts of Indonesia in the 16th century, but they were ousted by the Dutch (except in East Timor), who began colonizing the islands in the early 17th century. It would be the early 20th century before Dutch colonial rule was established across the entirety of what would become the boundaries of the modern Indonesian state.

“Japan occupied the islands from 1942 to 1945. Indonesia declared its independence shortly before Japan's surrender, but it required four years of sometimes brutal fighting, intermittent negotiations, and UN mediation before the Netherlands agreed to transfer sovereignty in 1949. A period of sometimes unruly parliamentary democracy ended in 1957 when President SOEKARNO declared martial law and instituted ‘Guided Democracy.’ After an abortive coup in 1965 by alleged communist sympathizers, SOEKARNO was gradually eased from power. From 1967 until 1998, President SUHARTO ruled Indonesia with his ‘New Order’ government. After street protests toppled SUHARTO in 1998, free and fair legislative elections took place in 1999. Indonesia is now the world's third most populous democracy, the world's largest archipelagic state, and the world's largest Muslim-majority nation.”

Source: U.S. Census Bureau, International Database (demographic data) and USA Trade Online (trade data); Central Intelligence Agency, The World Fact Book (country reference maps).