This is my first serious scenario. Since I had no prior experience, I decided to use real history as much as possible. Everything is as realistic as it could get, even down to which units are where and who attacks first.
England was split in civil war between the army loyal to Charles I (the royalists) and the forces of parliament (the parliamentarians or, as their enemies called them, the "roundheads). The war had gone on for two years now without a decisive victory on either side. Parliament created the "new model army", the first army where men advanced in rank on the battlefield based on fighting skill, not birth. Also, all of the men were trained instead of the peasent-militia that had fought in previous armies. Led by Oliver Cromwell, the new model forces marched in to battle near Naseby against the royalist forces led by Prince Rupert. The parliamentarian forces were proud of their training and confident that they could rise from simple farmer to colonel in such short time. The Royalists, on the other hand, had many hardened war veterans while many new model soldiers, especially the new model infantry, had never fought before. The new model troops had a terrain advantage but left it for an area where the Royalists would attack, just like Cromwell wanted them to. The stage was set for the battle that would change warfare into the buisness of skilled soldiers as well as crush the power of the English Monarchy.
My only hint is to follow the best moves of the real generals and correct their mistakes.