The evidence for the naval expeditions of the Chola rulers comes from the brief references in the eulogistic introductions of their inscriptions, very rarely corroborated by some literary evidence. From the early tenth century, the Chola kings took some military expeditions into Sri Lanka, obviously by carrying their warriors in boats across the Palk Strait or Gulf of Mannar. Here, of course, the sea distance to cross is only about 50 to 150 kms. If the Twelve Thousand Ancient Islands conquered by Rajaraja I is identified as the Maldives — and there is some good circumstantial evidence to do so (Nilakanta Sastri 1955, p. 192; Indrapala 1985, p. 51) — then this sea expedition was made over a distance of about 800 to 1,000 km. Therefore when Rajendra I sent his naval forces to the Srivijaya kingdom about 1026, the Chola navy already had some experience in travelling over long distances. But apart from these informed guesses, we have practically little explicit information from any contemporary source to understand the organization of the Chola navy, the nature of their sea vessels, the numerical strength of the warriors involved in the expeditions, or the port towns used as their naval bases.

It is a known fact that the history of medieval South India mainly depends on the contemporary inscriptions. True, there are several thousands of inscriptions in the south. The inscriptions, being mostly records of gifts of land, animals, gold, and other material to temples or other charitable institutions, give good information about the agrarian activities of the times, the temple rituals, and several aspects of religious culture. Some details about the society, economy, and the government of the day may also be gleaned from them. The nature of the inscriptions is such that we are not able to tell much about the science and technology of those times.

The eulogistic preambles of the inscriptions give some information about the personal achievements of the king and his retinue, the military exploits, the enemy countries that were attacked, and so on. But when it comes to the actual mode of land warfare, the strength of the army, the weapons that were used, and the mode of transport of men and material over long distances, the available information is meagre and fragmentary.