I have always been intrigued by the quote from the Earl of Orrery, who wrote in 1677 "We make warre more like Foxes than Lyons; and you have twenty sieges for one battel."
A few years ago I wrote a simple computer app which runs a mapless mini-campaign depicting a Vauban-style siege, where players are free to choose their own rules and armies to fight out the significant tabletop actions, but everything else is handled by the computer. The app essentially generates the narrative of a siege, and tells you what kind of scenarios to fight. All you have to do is command the troops in each particular action, and report back to the app who won – you can use skirmish-level rules, full battle rules, or any combination.
There are a set of random events, and between those and the outcome of various actions, the morale of either the besieger or the defender will eventually collapse. The siege can involve one single battle (an escalade up the walls) or involve several tabletop actions (the average is probably 3 to 6). The app generates a running log of the siege, which you can use to create your own after-action account with a little creative editing.
I have finally published the app for others to use (free of charge) – you can find it at:
link
(You can check it out by clicking through the game and just dicing for who won the tabletop actions – the whole thing will take less than 10 minutes, and you'll see how easy it is to use.)