Encyclopedia Barsoomia Wiki
The information in this article comes from Dynamites, warlord of mars and is not written by Edgar Rice Burroughs.

Rohn was a soldier in the army of Van Tun Bor at the battle of Thark. When it became apparent that the green hordes would overtake the city, Rohn was sent to warn the Jed so that the city could be evacuated before the greens arrival.  Rohn was hesitant to leave the battle, but he did as he was ordered.