The discovery of tin in Larut and rapid growth of the tin ore trade in the 19th century saw an increasing influx of Chinese labour. Later, rivalry developed between two Chinese secret societies. This, coupled with internal political strife between two faction of Perak's local Malay rulers, escalated into the Larut Wars in 1841. After 21 years of liberation wars, neighbouring Kedah finally freed itself from full Siamese rule in 1843, although it remained a Siamese tributary state until 1909. By 1867, the link between the Straits Settlements on the Malay coast and the British authority in India was broken, with separate administration and the transfer of the respective territories to the Colonial Office. The Anglo-Dutch Treaties of 1870–71 enabled the Dutch to consolidate control over Aceh in Sumatra. This later escalated into the Aceh War.