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With his transformation capabilities restored ( the explanation for which was not offered in the American series ), Grimlock was Optimus Prime's second in command in the so called Generation 2 series, aiding in the Autobots ' war against the " second generation " of Cybertronians led by Jhiaxus.

However, he remained as rebellious and aggressive as ever, though it proved to be a mixed blessing-at one point his urge to combat Jhiaxus's forces led him and his troops right into a trap, while at another time, his willingness to defy Optimus Prime's orders and launch an all-out attack saved Prime from certain death at the hands of Megatron.

When the Autobots and Decepticons united against Jhiaxus and the threat of the Swarm-a destructive by-product of Transformer reproduction-Grimlock was the joint leader of the ground troops as Prime and Megatron fought on other fronts, and survived the brutal conflict.