In October 1908, the first nationalist movement called Budi Utomo was formed. Four years later, on September 10, the first nationalist movement involving a significantly larger group of people was formed, titled Sarekat Islam. After the end of the First World War, the Dutch responded to these movements with repressive measures.
The nationalist leaders came from a group of young professionals and students. In the period of time after World War One, the Indonesian communists associated with the Third International started to take over the nationalist movement. The repression of the nationalist movement led to many arrests. Among those arrested was Indonesia's first president, Sukarno, who was imprisoned for political activities. Also arrested were Mohammad Hatta, the first Vice-President of Indonesia and Sutan Sjahrir, who later became the first Prime Minister of Indonesia.
In 1914, an exiled Dutch socialist, Henk Sneevliet, started the Indies Social Democratic Association. Initially being a small forum of Dutch socialists, it later evolved into the Communist Party of Indonesia, otherwise known as the Partai Komunis Indonesia (PKI) ten years later. In the post-World War I era, the Dutch strongly repressed all attempts at change. This repression led to a growth of the PKI in 1926, until 1927, the PKI led a revolt against the Dutch colonialism and the harsh repression based on strikes of urban workers. However, the strikes and the revolt was put down by the Dutch with some 13,000 nationalists and communists leaders arrested, out of which some 4,500 were given prison sentences.
Sukarno was released from prison in December 1931 but was re-arrested again less than 2 years later on the 1st of August in 1933.