The Army of Naples (French: Armée de Naples) was a French Army unit which took this name following its capture of Naples in 1799. It was related to the Army of Italy.
Barthélemy Catherine Joubert had just pacifed northern Italy. On 6 December 1798, Joubert occupied Turin, forcing King Charles-Emmanuel to abdicate, giving up all his continental possessions and retreating to Sardinia. Meanwhile, Grand Duke Ferdinand III's Tuscany was also occupied.
King Ferdinand I of the Two Sicilies, returning from Naples, ordered a massive attack on the French, but retired to Palermo at the same time. He named Pigantelli vicar general, but the city fought against him.
The army in Rome received reinforcements from Joubert, raising its strength to 29 battalions and 21 squadrons - a force of 24,000 infantry, 2,000 cavalry, and 2,000 artillery for a total of 28,000 men, including the garrisons of Ancona and Castel Sant'Angelo. On December 20, this army left Rome, which had been ordered to disarm, and advanced on Naples in five columns. Gabriel Venance Rey, who was already in pursuit of the enemy, took the right with twelve squadrons and twelve battalions. He had orders to advance to Terracina by way of the Pontins marsh. Jacques MacDonald with three squadrons and twelve battalions had orders to cross Frosinone and Ceprano. Jean Étienne Championnet and the headquarters followed this column. Louis Lemoine's division, six battalions and three squadrons strong, had orders to push on to Sulmona. Finally, the eleven battalions and three squadrons of the far left under Guillaume Philibert Duhesme had orders to push back the enemy at Pescara then follow the river of the same name up to Popoli and there rejoin Lemoine. There was too great a distance between the right and left columns. To remedy this, Championnet directed a column of 800 men under the orders of battalion leader Maréchal to take the route that goes from Tivoli and Vicovaro around Celano Lake to Sulmona. A camp was established at Foligno to meet this group in case of failure. The poor state of the roads was just about the only difficulty Maréchal faced en route. There was a small battle between his troops and those of the enemy on the 27th and 28th of December at the crossing of the Garigliano, but the Neapolitans fled in disorder after the first clash, abandoning all their artillery. On the 30th, MacDonald set up camp between Venafro and the road from San Germano to Capua in Caianello.