WARNING: The following contains spoilers for Episode 43 of That Time I Got Reincarnated as a Slime, now streaming on Crunchyroll.
In Reincarnated as a Slime Episode 43, Rimuru's international alliance prepares to meet Demon Lord Clayman's army on the battlefields of Eurazania while Benimaru the ogre leads Rimuru's coalition army on the front lines. This buys Rimuru time to crash the Walpurgis meeting to confront Clayman directly.
Demon Lord Clayman's army already marched on Eurazania once and crushed it, capturing Demon Lord Carrion in the process. Now, Benimaru prepares to turn the tables on Clayman's troops by preparing a deadly ambush for his 30,000-strong army, and not even Yamza, one of Clayman's Five Fingers, is ready.
Previously in Reincarnated as a Slime, when Rimuru became a True Demon Lord, his allies received new skills. Benimaru received the Born Leader skill, which allows him to coordinate Rimuru's massive army in battle. This, combined with Rimuru's mass teleportation spell, should make it easy to ambush Clayman's army and crush it. Meanwhile, the three Beastketeers serve as Benimaru's lieutenants, eager to fight for Carrion's behalf. Grucius, Phobio and Suphia aim to fight Clayman's most elite army leaders, including Yamza, Footman and Tear of the Moderate Harlequin Alliance.
All this proves the level of trust these warriors and leaders have for one another, uniting under Rimuru Tempest with the common goal of defeating Clayman and restoring peace for all monsters. Earlier, Rimuru's initial meeting with the Beastketeers devolved into a fight, but now the Beastketeers fight almost as loyally for Rimuru and Benimaru as they do for their own king, Carrion. Geld the orc leader fights with similar faith, setting up his men to pulverize Clayman's army with earth-based magic. The coalition's first major battle proceeds smoothly, reflecting Rimuru's leadership skills and the trust he earned from his diverse followers.
For the Beastketeers, this fight is personal, since Clayman had invaded Eurazania to harvest enough souls to become a True Demon Lord, and his followers Frey and Milim Nava fought and captured Demon Lord Carrion. Carrion is likely held captive in Clayman's castle while several of Rimuru's followers, including Souei, Hakuro and Shuna, plan to infiltrate Clayman's castle while Clayman is away to rescue Carrion. This is a rare opportunity that the ogres plan to exploit. That, combined with Rimuru's confrontation with Clayman, should bring him to ruin.
The battle proceeds as planned in the episode but Rimuru still has other problems, and the war with Clayman is likely to get messy soon. Clayman has possessed Milim with a necklace and she will likely come to Clayman's defense during Walpurgis against her will. Yamza will not go down so easily, even against Albis. There is also the matter of Demon Lord Cromwell, who correctly suspects Rimuru of blocking every nation's attempts to summon otherworlders. Cromwell may come to Clayman's defense against their common foe, Rimuru, and steer Walpurgis in his favor. If that happens, Benimaru's likely victory in Eurazania might mean very little. One battle won't necessarily decide Reincarnated as a Slime's war.