Gondor’s greatest maritime expansion took place under the period of the Ship-kings, who ruled between the ninth and twelfth centuries of the Third Age (830-1149). Their Númenorean ancestors, who had been great mariners in their time, were not forgotten by those in the South-kingdom, and as Gondor became more prosperous, the Dúnedain began to focus on sea power.
The first of the Ship-kings was the twelfth King, Tarannon, who constructed the first fleets and conquered the coastal lands to the south and west of the Mouths of Anduin. For his victories, he took the name Falastur (‘Lord of the Coasts’).
Succeeding Falastur, Eärnil I improved on his uncle’s work; he restored the ancient Númenorean haven of Pelargir upon Anduin and captured the rival haven of Umbar two years after taking the Throne. Twenty-three years into his reign, he was lost at sea.
The son of Eärnil I, Ciryandil became the third Ship-king for a time, before falling in battle at Umbar while defending the Haven against an attack from the Haradrim.
The fourth and final Ship-king, Ciryandil’s son Ciryaher became the most powerful ruler in Gondor’s history. Seeking to avenge his father, he began to reorganise Gondor’s armies and finally declared war on the forces of Harad, which were still attacking Umbar (despite having slain Ciryandil, they had failed to capture the haven). The Haradrim were defeated so severely that it took several centuries for them to regain their strength. The victorious Ciryaher took the title Hyarmendacil (‘South-victor’), and for 134 years reigned over Gondor.
With Hyarmendacil’s death followed the line of the Ship-kings; his son Atanatar (II) Alcarin, vain and lazy, neglected all that the previous Ship-kings had achieved, thus ending the line.