Booth's Escape Route

[wsanto]

I believe it is self-evident that Powell's motivation for attempting to assassinate Seward was his belief that he was fighting for a cause. And he was obviously convinced that this action would further the fleeting war effort of the South.

That said; I don't believe he was a soldier in the sense that he was directly ordered by a superior officer to assassinate Seward.

Powell got involved in Booth's plot to kidnap Lincoln. It may be that he was selected from the battlefield and put into the conspiracy by confederate secret service and/or military operatives. But as the plans escalated at the Herndon House in mid-April he took a step away from being a soldier and toward being an assassin. He took a step away from southern-gentleman soldier toward being a cold-blooded killer. He decided to take that step on his own.

He was not a cold-blooded killer until he took that step. However he justified taking that step that doesn't absolve him of full responsibility. He knew this himself and he bravely accepted his punishment.