How to run a siege ?


Banded Mongoose
Hi everybody,
I know, I'm asking again for your help about basic stuff, but for a future adventure, I have to run a siege.
So I'm searching some rule on how to treat invasive armies and defensive armies, I think that the walls and doors are already in the core book, I've found some siege weapons in Hawkmoon by Mongoose but not so much.
I'm taking all that you have to help me with this if you wanna help me.

Thanks in advance guys !
Humm, I have always just run it very openly.

First, decide how you want the siege to go before it begins, then allow the PC's actions to affect it. Unless they are AWESOME, it is unlikely that they can dramatically change the course of a siege involving hundreds or thousands of soldiers. The PCs can affect a local area/action, but rarely change the course of the war.

Sieges take a long time historically - most sieges were more like "surround them and starve them out" rather than actual "batter down the walls and storm the castle" although there were those too. Thinks weeks, not days...

Another important point is that the enemy is not stupid. If the PCs are using powerful magic, odds are the enemy has powerful magic too. Don't be afraid to overwhelm the PCs with a stronger enemy.

I read up on several historical sieges to get an idea of what is involved - Wikipedia helped there.
Work out how much food and water the beseiged have and how many days this will last.

See if the beseiged have a way of replenishing food and water, if so stopping them would be a scenario. If they have deep wells/ large cisterns then water might be OK, but food might be an issue. Find a way to get spies in to poison the wells. Catapult diseased corpses into the wells/cisterns.

Work out how many APs the walls have and what damage catapults do to the walls. Breaking a wall alows an attack to quickly break the siege.

How good are the beseigers at climbing? Using seige ladders and climbing the walls would give PC Adventurers a chance to be heroes, or to fall gloriously to their deaths. Work out how many climbing rolls are needed and who will be attacking them on the way up. Combat would then ensue on the walls as you try to protect the area to let others climb the ladders. Beware of boiling oil, I am not sure what the damage is but it is bound to hurt.

What about tunnels? tunneling below the walls and setting fire to pitch and straw is a good way of undermining the walls, or use oil or gunpowder. Miners from the beseiged place might send out countermines, to intercept you and collapse the mines. Someone with a Gnome would be very handy here.

Are there any weak points? Getting insiders to open little doors/gates is a tried and tested way of breaking a seige. Worming through a sewer or up a garderobe are smelly ways of getting inside. Having an expert climber climb a wall under cover of darkness or away from an attack is nother way of getting inside. If you have magic, then Teleport or Flight allows you to get quickly inside.

If you can't break the defences, then surrounding and starving them out works. However, both the beseiging and defending armies are liable to catch diseases. More than one beseiging army has been broken by dysentery or poor supply lines.

Unless the PC Adventurers are important, they won;t know what is going on. They will be told to build this, dig that, attack here and so on, It can be very frustrating being a soldier in a seige.
Don't forget treachery by someone inside and even honest negotiation for those players who prefer a more intellectual rather than violent way of ending things.

Believe it or not, despite all the military tactics available, the most successful sieges were those that ended with talking. Starvation was a gruelling prospect for the defenders (and boring for players), and assault equally unappealing to the attackers. Legend's combat rules can be rather vicious. Under accepted medieval rules of war, a town captured by force could be ransacked but one that surrendered could not. This encouraged agreements to surrender if the defenders were not relieved within a set amount of time. This, rather than an assault, ended some of the most significant sieges, such as Stirling in 1304 and Harfleur in 1415.
Rarely was a siege about killing everyone in the castle. Often it was about a single individual or group. A negotiated solution - I'll go with you but I get to keep all my lands and money and am treated like an honored guest until I can pay the ransom - it was a common solution.

Nobles buy their way out of problems, not fight it out.

A noble might even be willing to surrender the castle to an enemy, but get to stay in charge, reporting to the new boss...
If assault was easy against a supposedly prepared position and an aware adversary, no one would bother with sieges.

Risk reward would have to be worth it, either for an assault or a siege, because you don't want to find the positions reversed, such as at Alesia.
Which would be the most challenging - the players as besiegers, looking to scheme and connive their way into the fortification like dogs? Or the players stuck in the middle of the siege, rooting out spies, saboteurs and enemies scaling the walls, defending the wells and food reserves from those same spies and saboteurs - and also from the citizens?

The siege is something akin to a storm or a forest fire; something going on in the background. Player characters pursue whatever their goals are, carry out their assignments, and at one point the Gamesmaster decides that something changes.

What sort of things could change?

- The besieging encampment receives new food and supplies
- Food, water, medicines reach critically low levels in the besieged fortification
- The fortification is infiltrated
- The fortification is breached
- The besieged ruling body surrenders, the besiegers accept, the siege ends and the city begins a new phase as a subjugated people
- The besieged ruling body surrenders, the besiegers reject, offering far worse terms (e.g. send out all your women and girls to be sold as slaves)
- The besiegers tell the besieged ruling body what to expect, and the ruling body plans to put their population to the sword rather than live as subjects of the besiegers
- Winter comes, and the besieging army is forced to go home

Things like that.

Now go and read what Sun Tzu has to say about sieges in The Art of War.