Section 885, Article 87, Uniform Code of Military Justice, Paragraph 3C: Any person found guilty of desertion or attempt to desert shall be punished, if the offense is committed in time of war, by death or such other punishment as a court-martial may direct, but if the desertion or attempt to desert occurs at any other time, by such punishment, other than death, as a court-martial may direct.
Ideally he'll spend years in Leavenworth making little rocks out of big ones. In fact, he'll probably get a dishonorable discharge and little or no prison time