Battle of Evesham

The start

Simon De Montfort was on his way north to join forces with his son at Kenilworth, taking his captive, King Henry III, with him. 

Prince Edward (later Edward I), who'd also been a captive of de Montfort, but had escaped, intercepted him at Evesham.

At dawn lookouts for de Montfort's army, in the tower of Evesham Abbey, reported that the Royal army was at Green Hill, just outside the town. 

Vantage point from which the Royal army was seen

De Montfort's army found itself in a loop of the River Avon, with Edward's forces holding the high ground, and blocking off the only available bridge.

Despite being outnumbered by at least two to one, de Montfort decided to fight his way out, perhaps confident, because he'd already beaten a Royal army at the Battle of Lewes.

His troops left Evesham at about 8am, just as a violent thunderstorm broke.

This meant they were attacking uphill, in the wet, against superior forces.