The new army will firstly need to build up, so keep using your abilities to incite greater unrest within the town.(Important Note: As it builds up, the enemy may bring in reinforcements or another faction may try to take the town as a slave and/or rebal army will attract 'visitors' that may take the town before you, so watch out! If this happens, unless you want to take them on, just let them take the town and repeat step one.) When it feels confident to launch an attack, the new army will in most cases win if the battle is just against the local garrison. If it loses, just wait until it wins and takes the town. If it wins, the original faction that was there from the start of the campaign will take over the town, or if it's a town from the start, then a random new regional faction will spawn and take over the town. Regardless, any of the factions that take it over will have no allies or enemies, it's a clean start meaning they will also have spawned with two basic armies and a spy.