During the War of Vengeance in 2317, the 55th Imperial Army took part in the Attack of Feldirn with Leon II and the Aetherian Legions. Feldirn was held by Cain Velinmir and his vampire army for 6 years and Leon II needed Feldirn to launch the next phase of the campaign's plan. Thus, the battle began. Leon and Cain fought while the 55th Imperial Army was occupied with the rest of Cain's army.

The 66th Armored Division was being besieged heavily by vampiric and demonic infantry from the front. When the 66th was about to succumb to overwhelming force by the enemy, Commander Derec blew the Battle-horn and the 433th lead a massive tank charge. The loud horn confused the enemy and gave the 66th time to regroup. The 433th's armor swiftly pierced the unguarded enemy left-side and ran over their infantry. Their bodies and heads popping like meat-filled balloons under the sheer weight of the tanks. Imperial infantry in the rear of the charge were left with the task of gunning down any who weren't run over

Despite Leon II and the 55th Imperial Army failed to capture Feldirn during that time, the 433th Armored Division was given the name The Iron Horse Division for their brave charge at rescuing their comrade in the 66th.