The Sultanate of Siak Sri Indrapura, often called Sultanate of Siak (; Jawi: ), was a kingdom that was located in the Siak Regency, Riau from 1722 to 1949 CE. It was founded by Raja Kechil, who was from the Johor Kingdom (Sultan Abdul Jalil Rahmad Syah I), after he failed to seize the throne of the Sultanate of Johor. The polity expanded in the 18th century to encompass much of eastern Sumatra as it brought various communities under its control through warfare and control of trade between the interior of Sumatra and the Melaka Straits. The Dutch colonial state signed a series of treaties with Siak rulers in the 19th century, which reduced the area of state influence to the Siak River. For the remainder of the Dutch colonial era, it operated as an independent state with Dutch advisors. After Indonesia's Independence was proclaimed on 17 August 1945, the last sultan of Siak (Sultan Syarif Kasim II) declared his kingdom to join the Republic of Indonesia. History The history of Riau before Indonesian independence time has been rooted in the history of Siak Sri Indrapura, a Malay Islamic kingdom. The Siak-centred sultanate was founded by Sultan Abdul Jalil Rahmad Shah in 1722. The first Sultan died in 1746 and later posthumously given the title of Marhum Buantan. The reign was continued to Sultan Abdul Jalil Muzaffar Shah (1746–1761) who ruled for about 19 years. This second Sultan succeeded in making the Kingdom of Siak Sri Indrapura strong and triumphant. The third Sultan was Abdul Jalil Jalaluddin Shah (1765–1766) had only ruled for a year. His real name was Tengku Ismail. His reign was under attacks of the Dutch East India Company (VOC) which took advantage of Tengku Alam (later became the fourth Sultan) as a shield. Sultan Abdul Jalil later dubbed Marhum Mangkat di Balai. Tengku Alam (1766–1780) ascended to the throne after the death of Abdul Jalil Jalaluddin, with the title of Sultan Abdul Jalil Alamuddin Syah and posthumously given the title of Marhum Bukit. The daughter of fourth Sultan, Abdul Jalil Alamuddin Syah, Badriyyah was married to a person knowledgeable in Islam Sayyid Uthman bin Abdurrahman bin Sa'id bin Ali bin Muhammad bin Hasan bin Umar Banahsan, a Hadhrami of Ba 'Alawi sada family. Uthman was then appointed as a military commander and religious advisor in the Sultanate. Six of their descendants from this marriage became Sultans,