Lyric discussion by PTDean 

Cover art for The Tank lyrics by Dear Hunter, The

The band says that Act III tells of "the boy" going to war to forget about his history...but he meets a previously unknown half-brother (from his military father's wartime fling). His brother is killed in battle and the boy is enraged that his father shows no remorse for his bastard son's death.

In that context, I think he is comparing his father to the tank that killed his brother. A mechanical war machine, all about precision and dealing destruction around him, uncaring of lives lost as long as he continues his objectives.

My Interpretation