Not to mention dragons were most useful for intimidating and dispersing the enemy unless the battlefield wasn't an open area covered by dry grass. Even Balerion, who was more than a hundred years old, with the help of Meraxes and Vhagar, only killed four thousand out of fifty-five thousand men in the Field of Fire. Additionally, most of those deaths were due to the fire spreading because of the dry grass and not dragonfire directly. The rest of the enemies had deserted into the hills or surrendered. The North itself was cold and wet, and there were no fields of dry grass to burn. And while Winter was very formidable, especially after the rituals, he did not have more than a hundred years to grow like the Black Dread. And last but not least, there existed a real chance that he could set the surrounding wolfswood on fire, which was definitely not advisable either.