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Basic Information

Fortifications are buildings and structures built to provide defenses in time of warfare. The etymology of the term fortification is from the latin fortis facere "to make strong" and is, in brief, exactly that - a process of making an existing location into a strongpoint against attack.

The exact nature of a fortification will depend on what is to be defended, from whom, by whom and for how long and on what the builders have to work with in terms of technology, materials and other resources. A permanent, purpose build defensive position (such as a fort or castle) will vary greatly from defences that are added to an existing structure (such as city walls) and from temporary fortifications constructed on a battlefield.

Ideally the military engineer in charge of fortification gets to select a defensible position in which to build - historically, high ground was important (although it is more of a mixed blessing in the modern era) and limited approaches (due to water or other obstacles) were (and remain) beneficial as well. Of course, the defensive location must be near enough to influence whatever it is meant to defend - an impregnable position in the middle of nowhere is very little use to anyone1. Compromises may be required and, if possible the engineer may arrange to alter the ground to suit. The site should also have adequate supplies of water and whatever energy source the constructing civilisation uses, not to mention adequate sanitation2. Adding defences to an existing site is much harder - towns and villages (let alone cities) are rarely located anywhere defensible3 and even once built the defences must not interfere too much with the primary functions of the settlement.

Once the location has been chosen, the engineer has to turn his mind to who will occupy it - we've already touched on this in the matter of water, energy and sanitation4, but he will also need to consider living quarters, food storage and the like. The number and skill level of men available to man the defences will have a direct bearing on the design - for example if only a small, relatively unskilled garrison is available to man a given fort great care will need to be taken to protect the walls from escalade which would simply overwhelm them.

The nature of likely attackers should also be taken into account - if the threat is only from disorganised tribals, bandits and wild animals, the level of protection necessary will be much less than if they are to face regular troops supported by artillery and directed by a siege engineer.

The next challenge is to determine the materials of construction - and these will depend on the technology level of the builders, the materials available to them, the time and other resources that can be spared for the work and the threat to be faced. The most basic defences are those composed of natural materials to hand - drystone walls, ditch and rampart fortifications, rammed earth walls, abbatis and the like. For temporary, battlefield, fortifications they may be all that is required - and they may also be Hobson's choice if that is all that is to hand. A little more processing creates the palisade - where timber is freely available, or mud brick walls5 (generally in drier areas), alternatively earth fortifications can be faced with stone and/or re-inforced with timber beams in something like the murus gallicus style. Ditches can also be flooded to create a wet moat.

After that, things pass on to dressed stone - either a pure stone wall or, more commonly a wall composed of two faces of dressed and fitted stone with a fill of rubble (known as opus incertum). Fired clay bricks were also used in some cases, especially in places where local stone was of poor quality or inacessible. Stone walls - of various designs - were considered more or less the achme of fortification (albiet acheived with considerable cost and difficulty) until cannon started to dominate the battlefield. Ironically, the rise of cannon turned the clock back - more or less - to the era of rammed earth. The engineer could build walls of whatever he liked, but unless they were protected by a glacis an enemy gunner could flatten them in a few days. Along the way, the move from most soliders carrying melee weapons to most carrying ranged weapons - specifically guns - lead to the manned trench coming to dominate temporary battlefield fortifications and industrialisation lead barbed wire to replace a living abbatis.
The introduction of explosive rounds made even the the glacis obsolete - a fortification might be protected with layers of earth, but unless it was well built of reinforced concrete, exposive shells could collapse it. Put together, earth and concrete continue as mankind's best defence into the modern era.

Most of this, so far, has been about passive defences - obstacles and barriers - but only a little thought will show that a passive defence on its own is useless. Crossing an undefended obstacle is a trivial task in military terms - even a great river is nothing more than a delay if the crossing is unopposed. Even what are termed 'semi-active' defences - spikes, landmines, sentry guns and the like - can be easily reduced unless they are protected by active defences. Put simply, an active defence is something that deliberately counterattacks an attacking force and both inflicts casualties on it and interferes with its ability to reduce or overcome the passive defences. A garrison on the walls is the obvious example, but so are crocodiles in the moat or guard dogs prowling between your fences. The longer the reach of the active defences the better - ideally they will out-range the attackers and force them to do all of their work under fire, but few defenders are that fortunate. Defenders may be supported by sensor systems of various kinds - everything from geese upwards in fact - to detect and locate attackers engaged in stealthy operations around the fortifications. Historically some powers - such as Republican Rome and Sparta largely or entirely ignored passive defences in favour of a good active defence by their armies: defeating the enemy in the field meant that he never had a chance to attack their cities.

Looking to the future, it is hard to predict what the materials of construction might become - force fields perhaps, if these are practicable, but failing that new and better substitutes for concrete would seem the best hope.

In speculative settings, fortress builders must also account for whatever fantastic elements are common to their environment - be it teleportation (magical or scientific), flying6 and burrowing opponents, invisible and/or incorporeal attackers, nanotech weapons and other magic or high technology based measures. Writers and GMs alike will need to consider all of these as part of the general themes given above, noting that they can also contribute to the defence.

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Game and Story Use

  • In a battle situation, unless both sides meet in open terrain, there's a good chance that one side has thrown up some kind of defensive fortifications, even if it's only trenches and barricades.
    • And the attacking side will want to put up defenses of it's own.
    • As a rule of thumb, cavalry based armies are a lot less likely to build battlefield fortifications than infantry based ones.
  • The party might have to attack an enemy fortress
    • Or defend their own.
  • Don't forget, when your fighter reaches the 9th Level he gets to build a castle.
  • Note that fortifications should suit the place where they are built and the people who built them - if either is dissonant, it may be a sign of a writer who did not do the research … or equally (and especially if lampshaded) a sign that it was built by someone other than the current inhabitants.
  • A castle in an apparently stupid place may have a special role to play - perhaps as a treasure store or a prison. If it's an ancient ruin, (or just ancient) it may be an indication that something from a previous era is - or was - in the area … even just fertile farmland that has now become a desert or swamp.
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