Pietro di Calvacasa writes in his diary: OC 1549, March 28, Monday. On the road between Dicalla and Trocca. Canonnade is heard from the direction of Chielli-Forte. It is important to coordinate our march with the other half of the army, but it is also important that I lead the main contingent. Captain d'Arson is well versed in the art of sieges and I have complete trust in him. Currently our movement across the country is hindered by nothing, yet I fear that loyalist spies from the villages we cross would tell the Civita Maria garrison of our plans prematurely. This ruse de guerre we are conducting seems to have an easy chance of failure right now.
Calvacasa's three companies of foot, about 400 men in strength, march on the main road towards Civita Maria, passing one smaller fort. The fort does not have the range to fire its cannons on the road and is only guarded by one company of provincials. A small detachment of dragoons and militia is screening every possible path across the woodland to prevent messengers to Civita Maria and notify Calvacasa immediately if the provincials take action.
A mercenary Varangian unit, the rest of the dragoons and the Glambrian storming party besieges Forte Chielli, lying on the Flossian border at the foot of the Alps, in order to secure the hinterlands. this fort is garrisoned by one company of provincial Cacciatori and a half-company of provincials. The fort has only one ancient cannon. The siege is led by Captain d'Arson and his highest priority is to convince the company commanders that his plan will work. They have only one day to complete the siege and only one small-bore cannon. Fortunately there is an excellent firing position facing the fort's gate and the garrison is understrength to watch over the entire length of the wall.
The dragoons surge forward to draw the enemy's fire. The rebel cannon focuses on bashing the gate down with solid shot. In the cover of smoke and the woods to the east, the infantry units crawl forward and build temporary earthworks. Forty bandits join the storming party in hope of loot, bringing the manpower of the first wave to a hundred and sixty. Casualties are expected on the approach, but d'Arson hopes that the earthworks will keep it to a minimum. There is simply no time for a regular siege, but d'Arson knows that no relief force could approach on the narrow mountain roads, so the defenders are desperate.
The day's hardest work falls to the gunners on both sides. After some brief attempts at destroying the gabions protecting the rebel artillery, the gun in the fortress focuses on the earthworks. There is little success, and d'Arson is an excellent artillerist: the gate is destroyed and the storming party advances.
A group of fifty men in reserve meet them and try to bottleneck them, but the Glambrians are more experienced and their grenades and blunderbusses push the enemy back enough that more can move through the gateway.
The rebel cannon lands a shot near the fortress gun, killing one of its crew. The storming party scales the stairs leading up to the ramparts. The defenders are too thinly spread, but attempt to regroup at the gatehouse and the western bastion. A group of Glambrians capture the fortress commander, and seeing how futile any further resistance is with the gate open and still more enemies below the walls, he shouts the order to give up.
The besiegers lost thirty men overall, a very small number considering their task. The first wave lost twenty to musketry on the approach from the earthworks to the gate, and the Varangians lost ten when they launched their attack as the second wave. They did not have to reach the gate as the defenders yielded sooner.
The fortress commander is taken prisoner, the rest are offered to be disarmed and let on their way to the southern countryside. Some decide to stay and join the bandits. Most of them are Cacciatori, knowing both the country they are in and the way of irregular warfare. They won't be repaying their debt to the Crown for a while now: they have to stay with the highwaymen as an emergency reserve in Chielli. These fifty men will be enough to watch the road to Flossia right now.
After regrouping, the rebels prepare to continue their march towards Civita Maria. The road they are taking is unknown to the loyalists, a small path connecting villages. Traversing it will be slower than Calvacasa's route on the better southern road. The Count's plan is to draw out the superior enemy force, estimated to be about six hundred, from Civita Maria's defenses with his smaller contingent. The loyalists would engage his army, then d'Arson's force with the cavalry and the galloper gun would arrive from the north, right above the loyalists' right flank, and roll them up. All it takes is precise coordination of movement. As the Count wrote in his diary, it is a bold stroke, but without proper siege artillery, this was the best solution he could come up with.