There were no air marshals.
The person in front of the aggressor was very polite but insisted on his right to recline his seat, which made the aggressor even more out of control. The situation was getting out of control when other passengers started to heat up and shouting that he deserved a lesson right there.
The crew was amazing in calming everybody down, assuring the security will do the justice upon arrival in Doha and managed to convince the victim to move to a seat near the front and when this happened the aggressor then agreed to move to a seat in the back of the plane. Even after they were moved, the other passengers were shocked and took everybody a while before they calmed down.