Marco showed up at Marineford with the rest of the Whitebeard Pirates and their subordinate crews from the New World. He stated that, including him, all of the Whitebeard Pirates were ready to battle anyone who had dared to lay a single finger on Ace. When Kizaru tried to attack Whitebeard with an array of laser beams, Marco nullified the attack with his powerful Mythical Zoan-type Devil Fruit abilities. He then proceeded to attack Kizaru, and successfully kicked him a great distance to the ground, although the admiral did not appear to be seriously injured. 
Despite the drawbacks of limited armor and high fuel-consumption, the Kämpfer was still an incredible mobile suit. Due to its late introduction to the war, only a few units were ever produced. A single Kämpfer was fielded by Zeon's Cyclops Team during their infiltration of the Libot Colony in the neutral Riah Republic of Side 6 on the 20th of December, Universal Century 0079. This unit, piloted by an inebriated Mikhail Kaminsky , destroyed the entire Scarlet Team mobile suit squadron of the assault carrier Gray Phantom single handedly. It then faced its primary objective, the Earth Federation's RX-78NT-1 Gundam "Alex" . Despite completely destroying the NT-1 Alex's chobham armor and damaging the Gundam, the Kämpfer failed to disable it and fell prey to the Gundam's wrist-mounted 90mm gatling cannon, which proved effective against the Kämpfer's weak armor.