Nigel Camplin, 55, accused driver Colin Evans of "cutting him up" on a roundabout before setting off on a four-mile chase through Caerphilly.
Footage played to Cardiff Crown Court saw Camplin tell Mr Evans "I'm going to kill you" in a foul-mouthed rant.
Camplin admitted to dangerous driving and was given an eight month suspended sentence.
He was also banned from driving for 18 months.
The court heard Camplin, of Maesycwmmer, was a 20-year veteran of the Royal Corps of Signals with an "excellent service record" who suffered from post traumatic stress disorder.
Judge Jeremy Jenkins told him it was "dangerous driving to the extreme" and that people who behaved in such a way "deservedly go to prison".
He added: "You completely lost your self control and should not have been behind the wheel of your car."
A former soldier has avoided jail after his road rage was recorded on his own "dashcam".