The Chola dynasty was a Tamil dynasty which was one of the longest-ruling in some parts of southern India. The earliest datable references to the dynasty are in inscriptions from the 3rd century BC left by Asoka, a northern ruler; the dynasty continued to reign over varying territory until the 12th century AD. The heartland of the Cholas was the fertile valley of the Kaveri River, but they ruled a significantly larger area at the height of their power from the later half of the 9th century till the beginning of the 13th century Under Rajaraja Chola I and his son Rajendra Chola I, the dynasty became a military, economic and cultural power in South Asia and South-east Asia. The power of the new empire was proclaimed to the eastern world by the celebrated expedition to the Ganges which Rajendra Chola I undertook and by the overthrow after an unprecedented naval war of the maritime empire of Sri Vijaya, as well as by the repeated embassies to China. During the period 1010–1200, the Chola territories stretched from the islands of the Maldives in the south to as far north as the banks of the Godavari River in Andhra Pradesh. Rajaraja Chola conquered peninsular South India, annexed parts of what is now Sri Lanka and occupied the islands of the Maldives. Rajendra Chola sent a victorious expedition to North India that touched the river Ganga and defeated the Pala ruler of Pataliputra, Mahipala. He also successfully invaded kingdoms of the Malay Archipelago. The Chola dynasty went into decline at the beginning of the thirteenth century with the rise of the Pandyas, who ultimately caused their downfall.