Raja Mansur ascended to the throne at a very young age following the abdication of his father,
Abdul Jamil Shah I, who went into religious seclusion in 1495. As Pahang at that time was a Malaccan vassal, Sultan Mahmud of Malacca had sent his minister Seri Dewa Raja to install his preferred new ruler. Raja Mansur was selected and was styled Mansur Shah I. It appears he reigned jointly with his uncle,
Sultan Abdul Jalil. He had exercised authority over the young Sultan. The reign of the two sultans oversaw the restoration of ties between Pahang and Malacca, that were previously marred by diplomatic tension during the reign of Abdul Jamil Shah. In 1500, the two states cooperated to defeat an
invasion by the
Nakhon Si Thammarat Kingdom on the instruction of
Ramathibodi II of
Ayutthaya. It was the last Siamese attempt, of this period, to subjugate the southern Malay states. Following the death of his joint ruler and uncle,
Sultan Abdul Jalil, Sultan Mansur became the sole ruler and assumed full control in 1512. Earlier in 1511, the
city of Malacca was conquered by
Portugal, bringing the rule of the Malacca Sultanate to an end, and as such ended Pahang's status as a vassal. However, the
Portuguese still recognised Pahang as a vassal, on the pretext that the city is now under their control, and demanded tribute. Sultan Mansur refused to pay the annual tribute, which resulted in open warfare between Pahang and the Portuguese. ==Death==