The Battle of Tar Valon was a major engagement fought in the spring of 1000 NE between the White Tower Aes Sedai and the Seanchan. The battle proved to be the catalyst for the healing of the Aes Sedai following their year-long schism.
In the summer of 999 NE, the Aes Sedai became divided over what was later determined to be the illegal deposing of Siuan Sanche as the Amyrlin Seat and the raising of Elaida do Avriny a'Roihan to replace her. The sisterhood split into thirds, with one group remaining in the White Tower, another forming a breakaway colony of Aes Sedai in Salidar, and the other third remaining neutral or undeclared. The rebels raised an Accepted, Egwene al'Vere, to serve as a figurehead Amyrlin, but Egwene, with help from the deposed Amyrlin Siuan, proved a superior schemer and seized control of the rebels in truth as well as name. She eventually raised an army of 50,000 troops under Captain-General Gareth Bryne and ordered them to Travel to Tar Valon and lay siege to the city.
As part of the attempt to force the city to surrender, Egwene sealed Northharbor and Southharbor with chains of cuendillar, but she was captured during this exercise. She was declared a novice once more, but she refused to accept this, asserting that she was the true Amyrlin, and was frequently punished for showing disrespect to Aes Sedai and Elaida, whom she considered to be a false Amyrlin.
In one of her prophetic dreams, Egwene foresaw that the Seanchan would attack the White Tower, but her warnings were ignored at Elaida's order.
At the same time as these events, the Seanchan returned in force, launched a substantial invasion of the west and southwest of the continent, and overran Tarabon, Amadicia, Altara, and parts of Almoth Plain. With their goal of conquering the entire continent, it was inevitable that their path would eventually lead them to Tar Valon, but events convinced them to move up the timetable for their attack.
During the conquest of Ebou Dar, a number of Seanchan damane detected vast amounts of the One Power being channeled from a hilltop north of the city. Unknown to the Seanchan, this was a circle of Aes Sedai, Kin, and Sea Folk Windfinders using the Bowl of the Winds to restore normal weather to the world. The channelers fled using gateways, but fearing the Seanchan would be able to work out how to create their own, Elayne Trakand tried to unravel the gateway, instead causing it to explode, vaporizing all of the Seanchan on the other side. The use of the Bowl of Winds had also severely affected the One Power in that location, making using it there difficult.
The Seanchan concluded that the Aes Sedai had developed and deployed an incredibly powerful weapon capable of destroying vast numbers of their forces. Although the 'weapon' was not used again in the following months as their grip on the southwest of the continent hardened, its apparent existence remained a cause for concern. Suroth decided to develop contingency plans for a surprise assault on Tar Valon to capture or destroy this weapon and simultaneously leash or kill as many Aes Sedai as possible. After Suroth's fall from grace, the Daughter of the Nine Moons, Tuon Athaem Kore Paendrag, was made aware of the plan as well, and approved it in concept.
The decision to implement the operation was taken after the failure of negotiations between Tuon and Rand al'Thor. Tuon hoped that depriving his forces of this imaginary weapon and hopefully hundreds of potential Aes Sedai followers or allies would convince him to bow before the Crystal Throne, as was prophesied, although she later acknowledged it would be more likely to just harden their differences. Still, depriving al'Thor of valuable resources was considered a worthwhile goal.
Approximately one hundred to'raken and an unknown number of escort raken flew in stages from Ebou Dar to Tar Valon, across Altara, Murandy, Andor, and Caralain Grass. They carried approximately three hundred troops with them, comprising two hundred Fists of Heaven, fifty sul'dam/damane pairings, and five Bloodknives, elite kamikaze-like assassins. Travel time was several days. By resting in remote grasslands far from habitation, they avoided being seen along the way, or if they were seen there was no time to warn anyone.
At the time of the battle, there were approximately three hundred Aes Sedai, several dozen Accepted, and over one hundred novices in the White Tower. The city held approximately 30,000 armed men, but most of these were on station near the bridges, ready to repel any sortie from the besieging rebel army. As such, the Tower itself was comparatively lightly-defended.
The Seanchan launched their attack at night. Damane operating from to'raken-back blasted several holes in the side of the White Tower, permitting Fists of Heaven and damane to enter the tower above ground level. Simultaneously, several to'raken landed on the Tower roof and in the square in front of the main entrance. This three-pronged attack caught the Tower Aes Sedai completely off-guard and several sisters were killed or captured in the opening minutes of the attack. Inaccurate reports of Shadowspawn led to panic and hysteria in several areas until the sisters regained their composure and began a counterattack.
Unfortunately, the divisions fostered between the Ajahs by Elaida's acts worked against them, with many of the Ajahs working alone and not in concert with others. Not until Saerin Asnobar assumed command of the ground floor defense was order brought to the battle on that front. The ground floor assault was also disrupted by the arrival of several of the rebel troops led by Siuan Sanche, Gareth Bryne, and Gawyn Trakand, who scattered some of the Seanchan forces there and killed one of the Bloodknives.
However, the main defense was carried out by the captive Egwene al'Vere on the twenty-second floor of the Tower, where a major breach had been made. Although dosed with forkroot and unable to channel more than a trickle on her own, she organized the novices into a coherent defensive force and taught them how to link and form circles that the Seanchan could not break, rendering them immune to shielding and capture. She also showed them how to Travel and with the help of the Green Ajah Captain-General Adelorna Bastine used this ability to raid the White Tower's store rooms for sa'angreal. Egwene herself took possession of the White Rod, a sa'angreal of immense strength. Once so armed and having cleared several damane from within the Tower, Egwene began shooting down numerous to'raken. Once a third of the Seanchan raiding force had been destroyed, it was forced to withdraw.
Over thirty to'raken were killed in the attack, along with their riders and any passengers. Ten damane were taken prisoner and their sul'dam killed. At least one Bloodknife was also killed and for a period of time, the very existence of the remaining Bloodknives was a Seanchan secret. Other Seanchan losses are unknown, but the Fists of Heaven suffered heavy casualties within the Tower and in the battle before the main entrance.
Twenty Aes Sedai sisters and three novices were killed within the Tower. Almost forty initiates, including over two dozen full sisters, were captured by the Seanchan, including the Amyrlin Seat of the White Tower herself. However, it is possible some of the captured initiates were killed when their to'raken were shot down while trying to escape.
The capture of Elaida meant a shift in the White Tower's policy, allowing them to recognize and accept Egwene al'Vere as their Amyrlin Seat. This led to the end of the Aes Sedai civil conflict and the reunification of the Tower. Also, thanks to intelligence received from Verin Mathwin just prior to the battle, Egwene was able to expose almost all members of the Black Ajah within both camps, and a third of them were captured and executed before the rest fled. While the Seanchan attack was a devastating blow to the White Tower's image of invulnerability, it nevertheless unified the Tower after a long period of division.
Following the Battle, the surviving Bloodknives of the Seanchan force remained in the Tower in secrecy, preforming covert assassinations of sisters. Three Bloodknives were discovered and killed by Gawyn Trakand in a failed assassination attempt on the Amyrlin Egwene al'Vere.