Anger, although more metaphysical than gunfire, also seems naturally connotated with the color red. Perhaps these are angry, impassioned words or perhaps they are promises regarding his courage in battle. Either way, Crane's use of red or crimson literally colors their intention for the reader. He wished to rush forward and strangle with his fingers. He craved a power that would enable him to make a world-sweeping gesture and brush all back.
Physical injury is introduced most clearly in the book's title.
To face wounds in battle is every soldier's sentence. Fleming, however, thinks that a would will somehow indoctrinate him into true soldierhood, will combat his youthful anxiety. The red badge of courage is for those who survive. In fact, Fleming finds his courage in the end with out bodily injury. The red sickness is not an angry emotion, but rather a fear.