Siege (derived from the Latin sedere "to sit") is a form of warfare concerned with the capture and/or reduction of fortifications.
As the name implies, the simplest form of siege warfare is simply to surround the enemy position and wait until it runs out of food and/or water, gives up or is overcome by disease. This may take rather a long time and, given the rudimentary sanitary conditions and shaky supply trains of most armies into the very recent past, the attackers may well need to give up before the defenders.
For anything else, you probably need a siege engineer1 - or at least someone who can do a reasonable impression of one. Once he has arranged the siege camp so that it doesn't choke on its own sewage, his next move is likely to be to set up lines of circumvallation and countervallation (or contravallation) - fortifications which (respectively) face toward the besieged location (to prevent breakouts or less ambitious spoiling sallies by the defenders) and which protect the rear of the besieging force from any attempt at relief. Countervallation is only really necessary if the enemy have a reasonable chance of putting an army in the field and/or the besiegers are weak enough to be vulnerable to guerilla attacks. In the pre-gunpowder era these fortifications are likely to be palisades or similar works … afterwards, trenches are probable. Fortifications will also include emplacements for any artillery to protect them from counter-bombardment (if this becomes an issue).
This phase of the siege is known as investment and G. Julius Caesar's works at the siege of Alesia are probably a textbook example of this sort of thing.
If the investment fails to defeat the defenders, or cannot be achieved, or is simply expected to take too long, the besiegers are then left with two options, neither of which is exclusive of the other: either they attempt to reduce the defences, or they attempt to take the fortifications by assault. In general, both options will require siege engines (including or limited to artillery), although reduction by engineering is also an option (for example by undermining walls, cutting off the water supply2 or flooding the position). chemical or biological attacks may also be attempted.
Moving directly to assault is generally fairly costly in terms of lives unless some kind of trickery or exploitation allows a suprise capture of one or more parts of the defences (sometimes known as a coup de main assault) and so some amount of reduction (for example, breaching a defensive wall with artillery) will normally be attempted first. Limited reduction (for example filling a moat) may also be required to deploy adequate siege engines for an assault. Conversely, complete reduction is generally impossible and will certainly be slow and expensive to attempt - after which some kind of assault will usually still be required. Historically many sieges were resolved at terms once the defenders recognised that their casualties or reduction of their defenses had made their position untenable whilst other defenders handed over their positions once it became clear that they would not be relieved (whilst in others a strong or incompletely invested position held out for decades - for example a Selucid garrison held out in the Acra citadel in Jerusalem for over twenty years after the city itself was liberated in the Maccabean revolt). As against that, a garrison which refused to come to terms at a culturally agreed point was traditionally subject to massacre and/or enslavement (a tradition carried on by the Japanese Empire into the mid twentieth century). Cities that were taken by assault traditionally fared even worse with the population and their goods and chattles considered fair game for the assaulting troops.
Game and Story Use
- PCs can be on either side of a siege - and, especially as defenders of an improperly invested stronghold - can still get a great deal done.
- An interesting setting could place the PCs in a citadel, attached to a city that is more or less neutral to them and besieged by a third party (or, for a less complicated plot, a friendly city occupied by the enemy).
- Typical activities to include sallies (to destroy enemy siege engines or generally raid the siege camp), foraging for supplies and trying to arrange a relief (or at least reinforcements).
- Placing the PCs in the midst of a successful assault on a city might well be interesting - either on the defending side, trying to survive and escape during the sack (shades of the Aeneid perhaps?), or on the attacking side (or at least with them), trying to find something (or someone) in the chaos and prevent it being destroyed or stolen by looters.
- A large, long running siege can make for an interesting campaign background … bearing in mind that some ancient cities included substantial farmland within their walls and could hold out for years.
- And again with the citadel example.
- Siege warfare requires the sort of mindset that was not common amongst medieval generals - plenty of scope for hiring external consultants … or, as exemplified by the activities of King Stephen of England, half-hearted attempts broken off more or less and random.
- PCs can serve as consultants, recruit them … or kill them off, depending who they are working for.
- In a fantasy campaign, biological warfare may include ghoul or zombie plague and attempts at reduction may involve all sorts of magic. Conversely magic may be used to import supplies, reinforce defences or attack enemy siege engines.
- In many places, a siege may have a significant time limit for the attacker - even if no relief is expected, he must still keep his army in the field, fed and paid and disease free for long enough to reduce the fortification. In a feudal setting (for example) his feudal levies will either go home when their duty service ends or at least become a lot more expensive. Many tribal armies will fall apart due to boredom, bickering and factionalisation during a long siege and pretty much anyone who isn't a professional soldier will want to go home and get the harvest in sooner or later.
- Of course, this brings to mind a good feint. A feudal commander starts a siege and then orders his tenants to withdraw as though their service were up - the beseiged party then sallies out, finding that the beseigers no longer outnumber them and the beseiger then brings his tenants up from where he has hidden them or retreats towards them, pursued by an enemy with a false expectation of victory. Having won the sally battle he then either pursues the defeated enemy back into the castle and so takes it, captures or kills the castle's holder so leaving the remaining garrison with no reason to resist, or at the very least inflicts so many casualties that he can easily take the castle thereafter.
- If your system has strong morale mechanics, this is an ideal place to use them.