When Korra and Kuvira emerged from the portal, the suits' pilots assumed the Avatar had captured the latter and surrounded her. When Kuvira's dismounted energy cannon incidentally created an explosion that devastated downtown, creating a new spirit portal, Earth Empire mecha suits began searching the area for their leader. Another trio of suits cornered Prince Wu and a number of refugees, only to be taken out by two badgermoles Wu had tamed. A number of suits were disabled when Varrick created a larger electromagnetic pulse, though the giant mecha suit was unaffected due to it being powered by spirit energy. Kuvira's mecha suits began marching into Republic City to crush any resistance. Kuvira operated an enormous mecha suit, standing over twenty-five stories tall, to easily transport her spirit energy cannon. A giant version of the mecha suits was developed in secret by Kuvira's army armed with the spirit energy cannon, using platinum from the dismantled domes of Zaofu. When the Beifong family attacked the factory where the cannon was stationed, they defended it, though were toppled when Toph shifted the earth underneath their feet. Capable of lifting heavy objects, they loaded the weapon with the power core that contained the spirit vine sample. in his work on assembling the spirit energy cannon. ДЄs heavy machinery, the suits were also useful to aid Baatar Jr. They ran into some trouble, however, when the vines started to fight back, though by using their chainsaws and metal cables, the mecha suits were able to overpower the hostile vegetation. Kuvira led another battalion of mecha suits to the Foggy Swamp, where she ordered them to start harvesting all the spirit vines they could find at the base of the banyan-grove tree. Being superior in firepower and endurance, the suits pressed the benders back, though Varrick managed to immobilize them all with an impromptu-created electromagnetic pulse. When Bolin, Varrick, and several escapees from a reeducation camp attempted to pass the border, they were recognized and four mecha suits instantly surrounded them. The mecha suits were also deployed to guard the border posts of the Earth Empire. Д«eing electrically powered machines, mecha suits can be disabled by an electromagnetic pulse. The mecha suits tried to tie the flying bison to the ground by shooting grappling hooks at him, though the creature managed to take off in time. Before they could reach the women, however, Meelo swooped down on Pepper and barraged the suits with concentrated air blasts, pushing them back. Although the infantry was blown backward by the whirlwind Opal and Jinora created, the mecha suits managed to push through. When Opal and Jinora violated the peace agreement Kuvira had set up with Korra, she ordered her army to attack the Avatar and the two airbenders.

In the ensuing battle, Bolin's suit and those of the two sergeants were destroyed. and two army sergeants, who were also each piloting a suit. While debating on their course of action, they were ambushed by Baatar Jr. and two other soldiers of the Earth Empire.ДЄfter Bolin and Varrick became aware of Kuvira's darker nature, the two men and Zhu Li deserted the army, each securing a mecha suit to facilitate their escape. Zhu Li, Varrick, and Bolin got caught in a mecha suit battle with Baatar Jr. Upon their arrival, the pilots allowed children to play around in the vehicles. In 174 AG, after the governor of the Earth Kingdom state of Yi signed Kuvira's offer, they were deployed in the state's capital to secure the protection of its citizens. Kuvira's army employed several battalions of mecha suits.

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