You can add a little surprise, but only if it keeps the line of attack. The old plans are the framework that holds the army together; improvisation is the mortar that can turn the mortar into a grenade. Throw in a sudden feint, and you gain a tactical edge, but if you abandon the disciplined structure you risk chaos. So the best approach is to weave improv into a solid base, keeping the line tight while the surprise keeps the enemy off‑balance. That’s where old meets new, and that’s what makes a commander effective.