Alliance Remnants

The Alliance Remnants were a regiment of surviving Alliance troops under the command of Prince Kael'thas Sunstrider, but serving to the Grand Marshal Garithos. Their races consisted of humans, blood elves, and Bronzebeard dwarves.

Alliance with night elves
The Alliance Remnants were stationed throughout Silverpine Forest. Prince Kael'thas and his blood elves were located near the shores of the Great Sea and were attacked by the Scourge, they barely defeated that Undead group. They were overrun, however, and were preparing to leave when a group of night elves appeared, led by Tyrande Whisperwind and Maiev Shadowsong. With their help, the blood elves managed to avoid the Scourge at Silverpine, and continued their journey to safety. During the way, they fought against many undead groups and stopped at various blood elven towns to repair the caravan and to bring the elves living there with them. After some battles, they arrived to Pyrewood Village where they were ambushed by the Scourge.

The night elves and Alliance Remnants crossed the only bridge over the River Arevass, Tyrande Whisperwind defended that bridge but fell into its waters. Kael'thas was going to save her but Maiev Shadowsong told him to stop and help her to defeat Illidan. Kael'thas had to repay the debt to Maiev for previously protecting him and his people and left Tyrande to her fate.

Malfurion arrived at the base of the night elves and was informed of Tyrande's incident. Maiev told him that she was torn apart, but these were just lies. Kael'thas then came and met the leaders of the night elves and told them about Illidan's location. The Alliance Remnants defended the base from both the Scourge and Illidan's Naga, while Malfurion and Tyrande attacked Illidan. In the middle of the battle, a paladin named Magroth the Defender was rescued from the naga and helped in the battle. At last, Illidan was defeated, and when he was going to be executed, Kael'thas revealed that Tyrande may still be alive. Hearing this, Malfurion and Illidan decided to instead join forces to save her and found out about Maiev's lies. After that, the Alliance Remnants went to meet with the rest Alliance.

Blood elves imprisoned by the Alliance
Unfortunately for Kael'Thas, the battle in the Ruins of Dalaran had taken the time that the prince was scheduled to meet up with his commander. Kael'thas and the blood elves arrived with Lord Garithos and tried to apologize, explaining about the night elves, but the commander cut him off, telling the late prince that he was "not interested in your fanciful excuses." Garithos then charged Kael's unit with repairing three observatories, while continuing to insult the prince. The Alliance Remnants defeated demons and bandits and repaired one observatory but when they arrived at the shore they found out that the undead had destroyed the shipyard. Lady Vashj and her naga gave Kael'thas and his troops ships for free, after which the Alliance Remnants defeated an Undead Scourge base and repaired the two remaining observatories. Kael'thas reported his success to Lord Garithos, but Garithos told him that he shouldn't have accepted the alliance with the naga as they were inhuman.

Garithos left to the front lines and left Kael'thas behind waiting for orders. The next day he sent an emissary to tell Kael'thas that the observatories had detected a large undead army and the Alliance Remnants would have to defeat the undead before they could march on Dalaran. In addition, he was recalling all infantry, cavalry and support teams back to the front lines, leaving only the elven troops to fight. Once again, Kael'thas was forced to accept help from Lady Vashj and her naga in order to succeed. After their victory Garithos arrived with a great battalion of troops, accused Kael'thas of treachery and betrayal for once again siding with the naga, and imprisoned all the blood elves in the Dungeons of Dalaran.

Aftermath
By making those actions Garithos desintegrated the Alliance Remnants into two groups:
 * Kael'thas' forces, who went to Outland to join with Illidan.
 * Garithos' loyal human and dwarven troops that were called to the front lines, who were reintegrated into the Garithos' Enforcers and Garithos' Elite Guard. They were later mind-controlled by Detheroc and Balnazzar alongside the rest of the Alliance resistance in the Tirisfal Glades.

In the RPG
They were part of the New Alliance.