The Battle of Benevento was a conflict between the Carolingian Empire and the League of Napoli in the city of Benevento in the year 921. Following the loss of their capital and the betrayal of their ally, the Sicilian Emirate, the League of Napoli had faltered, leading to their inability to protect Benevento. This battle was seen as the beginning of the final plunge for the League of Napoli; the League lost this battle and the city of Benevento, allowing the Carolingians to successfully mount more invasions of southern Italy.
During the 9th century, Benevento had lost much of its power to the other Lombard nations in southern Italy. Combined with political and economic difficulties due to the Carolingians, Benevento became a puppet state of Capua. Due to their allegiance with Capua, they followed it into the League of Napoli. Following the Fall of Capua, however, Benevento was again independent, allowing it to somewhat regain its status in Lombardy. With Capua gone, it was only a matter of time before the Carolingians would mount an invasion of Benevento. Coupled with the betrayal of the Sicilians, Benevento's days were numbered.
Following the reclamation of the territories seized by the League of Napoli, Christophorus hoped to gain control of the League of Napoli or, at the very least, fracture it. Benevento was next on the chopping block for the Carolingian Empire after Spoleto was captured. An invasion along the border of Benevento in mid-921 was the herald to an attack on the city of Benevento. A full-on invasion of Benevento occurred in August of 921. By early September, the Carolingians were right at Benevento's doorstep.
An invasion from the north took Benevento relatively by surprise; the city-state was unprepared for the attack and resistance was relatively minimal. While Christophorus attributed the lack of preparedness to Benevento's decades of weakness, other generals suggested that Benevento had been abandoned by the League of Napoli. The Napolitan formations and defenses that were generally highly successful were easily toppled during this battle. By 9 September 921, the fighting in Benevento had stopped.
The loss of Benevento was seen as necessary by many Napolitan officials. Atenulf III, a native of Benevento, lost much influence with the League of Napoli, many seeing him as a traitor or a weakling willing to give his home to invaders. The damage to Benevento was relatively minimal, allowing the recovery effort in the city to take a much quicker time than in many other states.