The Battle of Shiloh (on Normal Difficulty) gives you far more troops than you need.
Pro Tips for this battle (on normal difficulty):
Don't over-engage or push too far
Hold Back
Keep a reserve
I kept facing the problem of being forced to retreat from engagements I had the upper hand in. I'm guessing that is normal on this difficulty.
What is this battle like on Legendary difficulty? The Battle of Shiloh (Day 1)