A judge told Ross Stewart that both of the attacks he perpetrated had "very serious consequences" for the victims.
Lord Turnbull told Stewart, 21, at the High Court in Edinburgh: "You have served your country well as a soldier."
The judge said it was clear he had developed post-traumatic stress disorder as a consequence of his experiences during active service.
He said he also accepted Stewart, a first offender, had recognised he had a problem and sought help.
The judge said these features marked him out from the violent young men he so regularly saw in court, and he could exercise a degree of leniency although Stewart's conduct was serious. But he added: "I would be in dereliction of my own duty if I did not impose a custodial sentence in your case."
Stewart had earlier admitted a serious assault on lorry driver John Malcolm, 25, at the Seaview Hotel, John O'Groats, Caithness, on December 31 last year.
Mr Malcolm suffered fractures to his cheekbone and eye socket and later had a metal plate inserted.
Stewart, based at Condor, at Arbroath, also pled guilty to a further serious assault on Philip Ablett, 50, whom he attacked on April 14 this year in Wick.
The attack victim had previously undergone a corneal graft to an eye following an accident, but it was dislodged in the assault.
Defence counsel Ronnie Renucci told the court as a result of the second offence Stewart was remanded in custody,where he was seen by a psychiatrist who diagnosed his condition.