Historically, what I am calling defence, combined policing and military functions in one role and were the responsibility of the local lord. In the Robin Hood stories, for example, ‘policing’ was carried out by The Sheriff’s Men while court cases were held by the local lord. Sure, the sheriff was appointed by the King, but then they had almost unlimited authority - certainly over all the non-nobles of the region. That pattern is common in European history – the local lord held their land because they promised to send troops to help the king in times of war - right up until scutage (the ability to pay someone else to do it for you) became common. Equally, they were required to maintain order in the are they controlled - and you can still see evidences of this in some UK placenames - Earl’s Court in London is an example of this. But it wasn’t just earls, every ‘lord’, right down to the lowest ranking knight, would have had their own courts. That even holds true in some parts of the world today. Afghanistan is a good example, where local warlords, and their troops, control the land, law and people.
In Britain, the first standing ‘state’ military unit, the Royal Navy, is credited to Henry VIII in the early 16th Century, the first standing Army is generally accepted a developing from the English Civil War, in the middle of the 16th century. Most of that war had been fought by regiments raised by wealthy landowners, under commission from either the King or Parliament - and very few of those combatants were trained soldiers at the beginning of the war.
These rules take elements of both of those scenarios.
Travel around the country is difficult - a few high level mages can teleport about -but just about everyone else has to travel on horseback or by boat - boat of which are notoriously slow forms of travel. The local guard commander can’t just check in with central command for instructions, they have to deal with it themselves. It can takes days to get even the most basic support and advice and weeks (or perhaps even months) for reinforcements to arrive. The Local Lord has to take responsibility.
For most of the game, Defence is about immediate, small scale, action or policing. In the countryside, the guards might catch outlaws, chase away a small band of goblins or deal with a wolf that is worrying sheep, and they might even chase them home to clear out the den. In a town, the city guard might break up a fight, stop a theft, break up a fight or cuff the ear of an urchin stealing bread - but they aren’t dealing with a regular, well drilled, army under the command of a general. In many cases, those guards also dispense small scale justice on their lord’s behalf, and the local guard commander is also the local magistrate. Longer term solutions, and larger issues, are a matter for the local ruler, be they the Local Lord or a City Council - a function that is measured by Stability under these rules. However, there are occasions when an area is attacked by foreign forces, or the King needs to wage a war on foreign soil – and these are both handled by Defence Points as well.
There are two basic positions - ‘at War’ or ‘at Peace’ – although the rules deal with three different wartime scenarios – Foreign War, Home War and Siege.
Hopefully, for most of the time your settlement or nation will be at peace. No one is seriously attacking you and you haven’t started a war with anyone else. Most of your troops will be redundant, and just carryout various peacekeeping and law enforcement activities. For most of the game, this is covered by the settlements Stability stat, and isn’t something that comes up in regular play. However, if PCs are causing trouble (fighting, rioting, stealing, killing etc) they will, most likely, start off by dealing with few individuals, rather than the army. This might be full-time members of the Town Guard (Warriors trained as Soldier Policemen) or Watchmen who have basic military training and minor weaponry (Warriors / Experts). If they can’t deal with the matter peacefully, the guard/watch will withdraw and call out a full unit of troops to deal with the matter. Rather than deal with these guys individually, I treat a unit of guards as a ‘compound encounter’, and play them as a swarm - with one set of attacks and one (high) number of hit points.
In this scenario, your King (or Local Ruler) has sent an army to attack another nation (or settlement). Obviously, you don’t want to send all of your troops, but part, if you are part of a larger state or organization, you will probably be required to send some troops to fight as part of the Foreign Army. This is the smallest part of your ‘army’, although it will probably include your ‘best’ troops.
If another nation is attacking yours, you will have an obligation to help defend the national boundaries and, probably, other settlements within them. While you don’t want to send all of your troops, you need to send more than you would to fight a foreign war. In some respects this is almost a policing action, and you will be expected to send the bulk of your fully trained troops to help defend the state. At its largest, the Home Army, consists of troops that could be sent abroad, as well as Town Guards, House Guards, Mercenaries units and just about any other fully trained troops resident or based in the nation.
If your town (or city) is under siege, with an enemy army camped in front of your gates – you are expected to throw everything into defence. Your Foreign and home army soldiers are supplemented by auxiliary troops and many of the concerned citizenry, who are not normally associated with the military, all helping to defend to the city walls. Everyone outside the walls, is brought inside the walls, and losses outside the walls are ‘accepted’ as part of the cost. If you have multiple walls, you can fall back if the outer walls are breached. If you have a castle, of a keep, at the center of your holding, that can be a refuge of last resort. If you are currently fighting a foreign war and (or) a home war your defences will be depleted, but you will still have some defences. If everyone is ‘home’ your city could be virtually impregnable.
All fully trained troops assumed to be Warrior-3 with light armour and military weapons. Some will have shields, some won’t. Unless players design their own troops, they will be assigned one of the standard troop types within the game. Regardless of actually build, all of these troops are treated the same way, when they are blocked together as a unit or an army.
Buildings with Def Points have staff to help in their duties, and they have some military experience, although not the same level as the main troops. Then there are always concerned citizens, some of whom may have good combat skills. They take their place in the town’s defences if they are attacked.
You can design your own troops, although they must be L3 and have similar equipment to the default troops. If you have more basic troops than you need to police your settlement , you can change some to light cavalry.
You can find a list of Standard Troop types on this page - Warrior-3, Light equipment worth (approx) 70gp
Every building with a defence value (regardless of type) comes with secondary troops as well. These are a mixture of hangers on, retired soldiers, auxiliary staff and militia members. These guys don’t go away to war, but they will help defend walls and gates if their settlement is attacked. While there might be a few warriors in the mix the majority are Experts, Aristocrats or Adepts, and (generally) aren’t as well traineds, or have the same equipment, as the regular troops described earlier.
Secondary troops aren't particularly relevant during peace time, BUT they help defend their town if it is attacked. This is relevant in the Mass Combat rules.
If you have more basic troops than you need to police your settlement , you may enhance some of your excess troops. Enhanced troops represent Veteran or Elite soldiers, who have served longer, are better combatants and have better gear. It costs 1bp to enhance a unit to Veteran status and another BP to enhance them to Elite troops.
Enhanced Troops don't make a lot of difference in peace time, but have an effect under the Mass Combat rules. However, they might be useful when dealing with monster incursions, misbehaving PCs, or their NPC equivalents.