The Lord Of The Ring: 10 Things You Didn't Know About The Fellowship
10. Aragorn Fought For Denethor's Father
Years before the forming of the Fellowship, Aragorn laboured long against the armies and allies of Sauron. He spent years traveling in the far east and south of Middle-earth, learning of Sauron's corrupting influence on the men of Harad and Rhûn. During his travels, he spent time in Rohan, serving King Théoden's father, and later the current Steward of Gondor, the father of Denethor.
At this time he was reluctant to openly declare his true identity, and went under the name Thorongil. He was considered a mighty commander by Denethor's father, and gained his trust quickly. He led an invasion by sea to attack the Corsairs of Umber, understanding they might be a threat during the coming war with Sauron.
His victory was praised, but soon after he left the realm of Gondor. The reason for this is twofold. Aragorn was also the Chieftain of the Dúnedain and he had many matters to attend to in the north. But he was also aware that the future steward, Denethor, had grown jealous of Aragorn. As his task was to unite the Men of the West for the coming war, he deemed it wise to leave before the tension caused a rift.
In the extended version of The Two Towers, Jackson included a scene which alludes to Aragorn's great age. Hinting that he served with Théoden when the King was only a small child. By the time of the movies, Aragorn would have been 87.