system
Given the following post, respond as if you're commenting on Reddit:
human
[Game of Thrones] How much of a gamechanger was a dragon on the battlefield from the arrival of Aegon as well as when Daeneyrs finally arrived to Westeros with her 3 dragons?
gpt
Really nothing in the modern or ancient arsenals could compete against a dragon. Hide all but impervious to harm. Able to crush several knights in plate armor with it's tail, claws, jaws, and it's own body weight. Can fly faster than any horse and most arrows. And flames so hot it can melt stone and steel like nothing and reach out quite far with it's breath. 

Outside of an errant trebuchet or catapult shot only ballistas pose any real threat to dragons and they're not known for their vertical aim. A dragon can outrun any serious trouble. Outflank any defensive line. And simply overpower nearly all enemies on the battlefield. One dragon can win a battle with ease. Multiple dragons can win a war. 

And given the unique capabilities of dragons anyone facing them will have to pivot all their efforts to wounding or forcing the dragon to retreat or risk being burnt to ashes long before any enemy soldiers can pose a serious risk. You either invest time and effort into countering dragons and get overrun by foot soldiers or focus on the foot soldiers and get taken out by the dragon. No one really could stop or win a fight against the dragons and the only reasonable options were to surrender or try to kill the dragonriders and hope it removed the beasts from the field which is still a longshot at best.