Battle plans often don't survive first contact
"You mustn't leave the field of battle until I say so," was the commander's first thought, but it didn't seem to match what took place on the battlefield.
What then, shall we just let them leave whenever they've had enough and decided the battle is over for them? Surely that would lead to an influx of trolls just log-jamming the system with immediate surrenders. What else is possible?
Examine the length of time before surrender for each contestant, and use that as a tool for matching players together. If there are people who surrender early then they can play against each other, while players who prefer endurance as a measure of merit can also face their peers.
http://img10.deviantart.net/e7f3/i/2015/316/5/7/jinx__by_ayyasap-d9geose.jpg