Whoever first said it wasn't a fair fight probably lost.
In war, the idea is to overwhelm your opponent to secure victory. This can be done in a variety of ways, such as by strength, stealth, or trickery. There are numerous strategies for dealing with an adversary, but they all have to be employed in real time. Most enemies don't wait for your to destroy them.
This brings me to a subject that deserves reflection for the warrior and his path: rules.
Rules in battle in this day and age are a romantic ideal by which we would all prefer everyone abide so as to decrease risk to the good guy in a particular conflict. Many of us, myself included, were brought up on the notion that the virtuous knight always overcomes the evil villian or evil dragon. We want to buy into the fantasy that because one is good, he wins.
Ultimately, good does win over evil. We know the end of the story, those of us who are Christians, but the truth is many good people have died to advance the eradication of evil. And it is troublesome.
We don't like this, but it is a fact. Sometimes evil people are better skilled or have better advantages that put our hero at risk. The warrior must face and acknowledge this so that any preconceived notions of wins in a conflict don't get in the way of his actual victory.
All that being said, fighting fair does not exist. There is no such thing. "What about sport? MMA or boxing?" you ask. "Those guys are tough." Yes, they are, but they are bound by the rules of an event, at a predetermined time and day. It's as much a psychological as well as physical display of combat, and it has its place. But the warrior's individual path should determine if that path is for him, but in reality showing up to an event to play by someone's rules reduces your chance of victory.
To increase your chances of victory, play by your own rules. Strike when least expected, where least expected. Take superior opponents by surprise. This is not cowardice, it is common sense. This is how a smart adversary thinks. He keeps an eye on the shadows, for at times he has been the one who lurks there.