The Battle of Cortenuova was fought on 27th November 1237 when Holy Roman Emperor Frederick II defeated the Lombard League.
The sources refer to 7000 - 10,000 Saracen archers, which intervened at the end of the battle - "emptying their quiver", as quoted by Pier delle Vigne - and probably saved the army from a repeat of the defeat at Legnano. This was a low point in the fortunes of the stubbornly independent city-states of northern Italy. The forces of the Lombard League were destroyed in the battle.
This was one of a number of campaigns by Frederick II against the Lombard municipalities during 1235 - 1239. These included the taking of Vicenza, the failure of the siege of Brescia and the battle of Cortenuova which established the reputation of the Emperor as a skillful strategist. He misjudged his strength, rejecting all Milanese peace overtures and insisting on unconditional surrender. It was a moment of grave historic importance when Frederick's hatred coloured his judgment and blocked all possibilities of a peaceful settlement. Milan and five other cities held out, and in October 1238 he had to raise the siege of Brescia.
The emperor then went on to invade the Papal States, and was excommunicated by Pope Gregory IX. It was a familiar experience for the former papal protégé.