It was fought between the Royal Sardinian Army – acting as the driving force in the war for Italian unification, against the Papal States.

[2] On 7 September, Camillo Benso, Count of Cavour, Prime Minister of Piedmont, sent an ultimatum to the Pope demanding that he dismiss his foreign troops.

[citation needed] The Papal army was composed of volunteers from many European countries, amongst whom the French and Belgian nationals constituted a Franco-Belgian battalion.

"[3] The Franco-Belgian, Austrian and Irish battalions later joined the Papal Zouaves, an infantry regiment of international composition that pledged to aid Pope Pius IX in the protection of the Papacy for the remainder of the Italian unificationist Risorgimento.

As a result of this battle, the Marche and Umbria entered the Kingdom of Italy and the Papal States were reduced to the area of what is today known as Lazio.