For the little story ...
At the beginning of XIX century, the kingdom of Piedmont-Sardinia decides the construction of a set of fortification to prevent a possible French invasion, the Barrière de l'Esseillon.
Between 1830 and 1860, five forts were built on the site of Esseillon, so Fort Marie Christine, the fortification dominates all 4 other forts, And the village of Aussois.
In 1860, the annexation of Savoy to France, then the breakthrough of the Frejus rail tunnel (commissioned in 1871) completely changed the strategic data: the forts lose their usefulness and will have then only a limited utility .
I suggest you making a voucher in alternative past, in which after X events, the French troops find themselves blocked at the foot of the barrier of Esseillon. with no other choice but to assault the fort in very rough weather conditions... Having very few artillery, the French troops will have other choices only to attack the garrison in the bayonet ....
To bring to a successful conclusion the attack, you have 4 pieces of ordnance among which howitzers 2, to use explosive charges maybe one the more but the more to risk for the troops.
Your scouts indicate you that several manners to attack are possible: by the main entrance, by the hidden door in the ditch , either by the tunnel acessible since one of the casmates. or you can hope to make a breach in the wall with your artillery !
Gamemode : Siege
Link : http://www.mediafire.com/file/ol898mj07njipvd/%5BSiege%5D%20Fort%20Marie-Christine.rar