system
Given the following post, respond as if you're commenting on Reddit:
human
[General Fantasy] How do you defeat a dragon on a battlefield.

I, the King, have received a challenge from the local dragon in the mountains. The dragon wants to fight and whoever wins gets all the others gold. How should I proceed? Assume I have as many resources that are needed.
gpt
Your Majesty, an ancient principle of strategy is to never give your enemies what they ask for. Anyone who invites you to duel does not have your best interests in mind. 

Dragons can fly. Their strength far exceeds that of a man. They breathe fire, and their skin is tougher than the finest armor. 

There is no fair wager of battle against a dragon. 

The strength of men is in our tools, our skills, in the discipline of our armies, one of which you lead. This is a plot intended to lure you into his kind of fight rather than ours. 

Reject the invitation. 

If you feel you must accept, name a time far in the future. Aquire the best rampart crossbow you can find, and practice with it. You will need reach and power above all else. No armor on Earth is strong enough to endure dragon's breath, and no man is swift enough to evade it. 

Your only chance is to strike first, and that must be lethal.