Ride of Eorl to the Battle of the Field of Celebrant
Event Type: Military/Strategic
Age: 3rd Age - The Stewards
Dates: April 6, 2510 ~ April 15, 2510
An event in the Invasion of Calenardhon by Balchoth and Orcs; see that entry for a description of the enemy and the overall timeline:
The invaders overran Calenardhon, and Cirion, Steward of Gondor, sent north for help; for there had been long friendship between the Men of Anduin's Vale and the people of Gondor. But in the valley of the River men were now few and scattered, and slow to render such aid as they could. At last tidings came to Eorl of the need of Gondor, and late though it seemed, he set out with a great host of riders.
The Return of the King, LoTR Appendix A, Annals of the Kings and Rulers: The House of Eorl
The first pair of messengers left on the tenth day of Súlimë; and in the event it was one of these [Borondir], alone of all the six, who got through ... He came at last to the Éothéod after fifteen days ... and he was so spent that he could scarce speak his message to Eorl.
It was then the twenty-fifth day of Súlimë. Eorl took counsel with himself in silence; but not for long. Soon he rose, and he said: "I will come. If the Mundburg falls, whither shall we flee from the Darkness?" Then he took Borondir's hand in token of the promise.
Eorl at once summoned his council of Elders, and began to prepare for the great riding. But this took many days, for the host had to be gathered and mustered, and thought taken for the ordering of the people and the defence of the land. At that time the Éothéod were at peace and had no fear of war: though it might prove otherwise when it became known that their lord had ridden away to battle far off in the South. Nonetheless Eorl saw well that nothing less than his full strength would serve, and he must risk all or draw back and break his promise.
At last the whole host was assembled; and only a few hundreds were left behind to support the men unfitted for such desperate venture by youth or age. It was then the sixth day of the month of Víressë. On that day in silence the great éohere set out, leaving fear behind, and taking with them small hope; for they knew not what lay before them, either on the road or at its end. It is said that Eorl led forth some seven thousand fully-armed riders and some hundreds of horsed archers. At his right hand rode Borondir, to serve as guide so far as he might, since he had lately passed through the lands. But this great host was not threatened or assailed during its long journey down the Vales of Anduin. Such folk of good or evil kind as saw it approach fled out of its path for fear of its might and splendour. As it drew southward and passed by southern Mirkwood (below the great East Bight), which was now infested by the Balchoth, still there was no sign of men, in force or in scouting parties, to bar their road or to spy upon their coming. In part this was due to events unknown to them, which had come to pass since Borondir set out; but other powers also were at work. For when at last the host drew near to Dol Guldur, Eorl turned away westward for fear of the dark shadow and cloud that flowed out from it, and then he rode on within sight of Anduin. Many of the riders turned their eyes thither, half in fear and half in hope to glimpse from afar the shimmer of the Dwimordene, the perilous land that in legends of their people was said to shine like gold in the springtime. But now it seemed shrouded in a gleaming mist and to their dismay the mist passed over the river and flowed over the land before them.
Eorl did not halt. "Ride on!" he commanded. "There is no other way to take. After so long a road shall we be held back from battle by a river-mist?"
As they drew nearer they saw that the white mist was driving back the glooms of Dol Guldur, and soon they passed into it, riding slowly at first and warily; but under its canopy all things were lit with a clear and shadowless light, while to left and right they were guarded as it were by white walls of secrecy.
"The Lady of the Golden Wood is on our side, it seems,” said Borondir.
"Maybe," said Eorl. "But at least I will trust the wisdom of Felaróf. He scents no evil. His heart is high, and his weariness is healed: he strains to be given his head. So be it! For never have I had more need of secrecy and speed."
Then Felaróf sprang forward, and all the host behind followed like a great wind, but in a strange silence, as if their hooves did not beat upon the ground. So they rode on, as fresh and eager as on the morning of their setting-out, during that day and the next; but at dawn of the third day they rose from their rest, and suddenly the mist was gone, and they saw that they were far out in the open lands. On their right the Anduin lay near, but they had almost passed its great eastward loop, and the Undeeps were in sight. It was the morning of the fifteenth day of Víressë, and they had come there at a speed beyond hope. 
Unfinished Tales, Part 3, Ch 2, Cirion and Eorl and the Friendship of Gondor and Rohan: The Ride of Eorl
1. In nine days they had covered more than five hundred miles in a direct line, probably more than six hundred as they rode. Though there were no great natural obstacles on the east side of Anduin, much of the land was now desolate, and roads or horse-paths running southward were lost or little used; only for short periods were they able to ride at speed, and they needed also to husband their own strength and their horses', since they expected battle as soon as they reached the Undeeps. [Author's note.]
Unfinished Tales, Part 3, Ch 2, Cirion and Eorl and the Friendship of Gondor and Rohan: Notes, Note 30
[Note: the dates were set by directly translating Víressë to April; no attempt was made to adjust for the differing lengths of the months.]
Elena TIriel 7.25.04