The Iron Cross Corps are Count Brocken's footsoldiers. Unlike the Iron Masks used by Baron Ashura, there is no clear indication of the origin of creation; but in the original manga it is implied that some Iron Crosses are brainwashed people that Brocken personally recruited.
The Iron Cross resemble Nazi soldiers wearing the Iron Cross on their helmets. Their eyes are solid black and combined with the masks they wear, their faces resemble skulls. In the anime their eyes are larger than normal and are googly.
The Iron Cross show absolute loyalty to Count Brocken, never questioning his authority. Some of them are much more heavily devoted to him and even try to kill Baron Ashura in the anime, something Brocken never wanted.
The Iron Cross are given weaponry such as rifles and other military weaponry which combined with their routine movements make them as skilled as regular footsoldiers but also more predictable.