I liked Trigger, but he didn't contribute all that much to horses or world history. It skipped famous war horses (Traveller
?) and largely ignored any 'history' that occurred before the author's birth.
"...Such a picture would inspire a poet, whose genius could then depict his worth, and describe his endurance of toil, hunger, thirst, heat and cold; and the dangers and suffering through which he has passed. He could dilate upon his sagacity and affection, and his invariable response to every wish of his rider. He might even imagine his thoughts through the long night-marches and days of the battle through which he has passed
... — Robert E. Lee