This map shows the forces of Gondor using white arrows, and the invading Wainriders in black. Green arrows represent the Northmen of Rhovanion, allies of Gondor.¹

(1)	King Narmacil II leads out the armies of Gondor and their allies to meet the invading Wainriders on the plains southward of Mirkwood.
(2)	The main battle is a decisive victory for the Wainriders; King Narmacil is slain, and the Gondorians are forced into retreat.
(3)	With the Northmen forming a rearguard, the surviving forces of Gondor escape southward into Ithilien.
(4)	The Northmen eventually flee the enemy; one branch escapes northward, eventually reaching Dale, where they merge with the Men who dwell there.
(5)	The greater part of the Northmen follow their leader Marhwini into the Vales of Anduin, where they give rise to the people known as the Éothéod.

The opening battle of a series of wars in which the lands of Gondor were assailed by the Wainriders, a force of peoples out of the distant East. Well armed and equipped, this people rode great wagons and chariots into war, representing one of the most dangerous enemies that Gondor faced during its long history.

The Battle of the Plains

In the year III 1856, Narmacil II had been King of Gondor for just six years when the Wainrider threat emerged from the lands eastward of Mirkwood. Narmacil's allies, the Northmen of Rhovanion, brought warnings that the invaders were planning to cross the Undeeps and raid into Calenardhon, and the King made plans to intercept them. At the head of his army, and joined by the Northmen under their chieftain Marhari, Narmacil rode out to intercept the oncoming force on the plains to the south of Mirkwood.

The battle was a disaster for Gondor. The King was slain and his armies defeated, and only through the valiant rearguard action of the Northmen under Marhari were even a remnant of Gondor's forces able to escape back into Ithilien. The Northmen themselves were scattered far and wide, and many were forced to retreat northwards. Some of these escaped as far as Dale, while others eventually settled in the Vales of Anduin, where they would give rise to the people known as the Éothéod.

After the Battle

The Battle of the Plains left Gondor greatly weakened, and its holdings beyond Anduin now dwindled to the narrow land of Ithilien between the Great River and the Mountains of Shadow. With Narmacil II lost in the battle, his son Calimehtar became King of Gondor, and the new King began to plot his revenge against the powerful foe. It would be long before he was able to build the strength to do so, but in III 1899 - more than forty years after his father's death - he was ready to make the attempt. Once again aided by the Northmen, Gondor's armies marched out to challenge the Wainriders, and after a hard-fought battle Calimehtar was able to claim victory.

Calimehtar's victory dealt a blow to the Wainriders, but they were not destroyed. Taking decades to regroup, they allied themselves with the Men of Khand and of the Harad, and planned a simultaneous invasion of Gondor from both the north and the south. By this time - the year III 1944 - Calimehtar had been succeeded his son Ondoher, and King Ondoher split his army into two forces to meet the double attack. The Southern Army, led by Eärnil, succeeded in defeating the Haradrim, but the Northern Army suffered a calamity. The King and both his sons were slain in the fighting, and the Wainriders won the field. The invaders thought that Gondor had been entirely defeated, and were feasting in their camp when Eärnil brought up his Southern Army and, in a sudden surprise attack known to history as the Battle of the Camp, utterly defeated the Wainriders.

Thus Gondor was saved, and the Wainrider threat eliminated after nearly a century of fighting. Nonetheless, the cost for the South-kingdom had been immense; two Kings - Narmacil II and Ondoher - had been slain in the wars, and the final confrontation had also seen the loss of both the heirs to the Kingship. After much deliberation, the victorious general Eärnil - who had some measure of royal blood - was given the Crown of Gondor. At this point, however, the Kingship of Gondor was nearing its last days, and only one other King would hold the southern throne before the line came to an end.