— Hartmann's breakdown after begging for Kertz to return them to the bridge.
Despite being referred to as a man by the rest of the crew, Hartmann has a very young appearance. Both he and Schröder were not mentioned during My Country Calling, and so are presumed to be relatively recent additions to the crew. Hartmann is a nervous wreck, wracked by tremors even when out of combat. In battle, he frequently panics at the sight of the enemy or when the Tiger takes damage. He also prone to outbursts, such as when he suddenly begs Müller to abandon their mission and return to the bridgehead. His fragile temperament is noted by Müller and rest of the crew with Hartmann being called "damaged" by Schröder. Kertz is more sympathetic and comes to his defense, and while initially agreeing with Schröder, Müller is hit especially hard by his fate.
Hartmann is first seen anxiously awaiting news while clearing Tiger 237 of empty shell casings, one of which he drops due to intense hand tremors. As they move out, he questions the fate of a group of Germans being led away at gunpoint, with signs denoting them as traitors and deserters around their necks.
During the battle towards Schimek railway, Hartmann frequently voices his anxiety about the enemy being too numerous and is either browbeaten by Schröder or reassured by Müller. Each time he receives an order from command over the radio, he must be prompted by Müller to respond affirmatively. At one point, he breaks down and begs Kertz to return to the bridge. Despite his protests, the crew continues their mission.
After the Tiger is attacked by rocket-firing Mosquitos and forced to hide beneath a ruined building, Hartmann is instructed to inspect the tank for damage while the rest of the crew decide who should be sent outside the tank to scout out an exit. Schröder argues that Hartmann, being unhinged and the only non-essential member of the crew, should be it, while Kertz objects believing him to be "in no fit state" to carry out such a dangerous mission. Following a moment of hesitation, Müller orders Hartmann to leave the tank. He strongly refuses, pleading with his commander using his first name and simply offering the excuse that "he can't". Müller appeals to his sense of duty, and Hartmann gingerly ventures out watched by his fellow crew until they lose sight of him. The crew waits for him to reappear, with Schröder branding him a deserter until the sudden arrival of a US Army tank column forces them to escape their hiding spot, leaving Hartmann behind.
Later as the crew rally at the final defensive line around the cathedral, they come across the group of German deserts, now hanged from lampposts. Amongst the dozens of bodies, Hartmann hangs from an arched street sign over a road; who is himself labelled as a deserter. While Schröder reaffirms his belief in Hartmann's cowardice, Müller snaps at him to shut up, stating that Hartmann did his duty.