The Númenórean who would be known as Tar-Ciryatan was born during a tumultuous time across the Sea in Middle-earth. The One Ring had been forged just decades before his birth, and during his youth the War of the Elves and Sauron raged across Eriador. Though the Númenóreans dwelt beyond the Great Sea and were thus isolated from this War, they came to play a part in the conflict. Tar-Ciryatan's father Tar-Minastir was instrumental in bringing the War to an end when he sent a great force into Middle-earth that succeeded in driving Sauron back to Mordor, though this fleet came too late to save the land of Eregion and its people.
It is unclear whether the future King Tar-Ciryatan played any direct part in these momentous events, though the fact that his name is never directly mentioned implies that he did not. Nonetheless he seems to have been influenced by the great victory of Númenor's navies, as he dedicated himself to the building of ships and the exploration of the seas around Middle-earth. Eager for power, it is said that he forced his father Tar-Minastir to resign the Sceptre early, an act that was seen as the first foreboding of the dire actions of the later Kings. Taking the Sceptre in the year II 1869, the new King chose the royal name Tar-Ciryatan, where Ciryatan (meaning 'shipwright' or 'shipbuilder') reflected his passion for sailing and exploration.
Tar-Ciryatan was a proud King, and where his forerunners had done what they could to aid and teach the people of Middle-earth, the new King saw their lands as a resource to be exploited. Under his rule, the Númenóreans began in earnest to establish ports and fortresses along the coasts of Middle-earth. Meanwhile Tar-Ciryatan sent his mariners across the Sea to extract the wealth of the Great Lands, and to demand tribute from the people who lived there.
These actions are generally seen as the first signal of the coming shadow on Númenor, and they also had one important effect in Middle-earth. The Dark LordSauron, whose defeat by Tar-Minastir had left him weakened, withdrew before the advances of the Númenóreans. In this time he worked to build his power in the eastern lands, far from Middle-earth's coasts, while nursing a hatred of the incoming Men of the West.
It was during Tar-Ciryatan's reign that political divisions began to arise in Númenor that would have a significant part to play in its later history. In his time the party of the King's Men emerged, abandoning the Elvish speech that had been used in the royal household throughout Númenor's earlier history, and privately using names in their own Adûnaic tongue (the name Tar-Ciryatan translated as Ar-Balkumagán in this language.) At this early stage, however, the division was not so great as it later became, and Elvish was still used in official documents such as the Scroll of Kings.
Tar-Ciryatan's name is interpreted as 'King Shipwright' in notes reproduced in volume XII of The History of Middle-earth. The meaning 'Shipwright' was shared by the name of another important character: the Elf known as Círdan the Shipwright. Indeed, these two individuals have essentially the same name in different variants of Elvish, one in High-elven (Ciryatan) and the other in Sindarin (Círdan).