Never let the AI control your reinforcements! The AI is stupid beyond belief: what kind of "intelligence" sends almost always sends the general careening through a wall of spears???

I've had the AI completely ruin carefully put together, veteran armies that, if used with ANY kind of intelligence, would have wiped out the enemy army without breaking a sweat. Instead, the AI will commit them piecemeal (with the general being first) and forget about elephants or chariots; if you give the AI control of these type of troops, they will run over your entire army to get to the enemy.

Whenever I fight any kind of battle, I will move all other armies far away so the AI won't ruin my silver/gold chevron armies that took me many, many turns to get them that experience.