-1

A common criticism I hear of fiction set in medieval-esque worlds is that it makes no sense for the defending army to leave the fortifications in order to meet the attacking army on the battlefield. In relation to this, I've heard "one man in a castle is worth 20 men outside it".

If this is the case, what reasons could lead to two armies meeting on the battlefield? I'd assume that, given the superiority of staying within the fortifications, warring on the open battlefield was a seldom occurrence?

Improve this question
6
  • 3
    I'm afraid this is far too broad. You could start by looking at List of battles 301–1300 and List of battles 1301–1600 for 'how often', but the 'why' would fill several books.
    – Lars Bosteen
    Commented Feb 25, 2022 at 1:23
  • 5
    Also, the HSE posts Why bother attacking castles at all? Why not go around? and Were any fortified castles self-sufficient in food? should prove useful.
    – Lars Bosteen
    Commented Feb 25, 2022 at 1:23
  • 1
    @LarsBosteen Thank you, those did help. Don't quite get why this is too broad however? Surely a list of categories of reasons could be made. Category one: "Garrison had to leave castle due to living conditions (like starvation or maybe sickness), battle ensued". Category two: "Incompetent leadership". Etc. Surely all that nuance that could fill a book can be synthesized into a few categories?
    – user110391
    Commented Feb 25, 2022 at 1:43
  • I would suggest editing part of your comment on reasons into your answer and perhaps delete the 'how often' bit (?)
    – Lars Bosteen
    Commented Feb 25, 2022 at 2:00
  • 1
    To understand why it is too broad, skim Brett Deveraux - just to understand the different periods and goals of siege warfare. I think he expliciitly answers your question, but neither the question, nor the answer are simple. In most games a siege is successful unless relieved.
    – MCW ♦
    Commented Feb 25, 2022 at 2:01

2 Answers 2

Reset to default
4

I see. Is this the only reason, though?

No, of course not. Fundamentally the reason to have an army is to achieve strategic goals. Only a small subset of strategic goals can be fulfilled by defending in a siege. As a general principle, you cannot win by defending. As Brett Deveraux points out in his articles on siegecraft, once the siege is invested, what remains is to negotiate the conditions of surrender. Meeting the enemy in the field of battle is a tactic in that negotiation. If you believe you can inflict disproportionate losses, or if meeting the enemy with disrupt their investiture of the siege, it makes sense to do so.

Sallies - "meet the enemy in the field of battle" can be misleading. It may make sense for the defenders to sally forth and raid against the attackers, then retreat back to the castle in a form of asymmetric warfare.

If the siege is about to be relieved, (allies come to support you against the besieging forces), then it makes sense to sally forth and meet the besieging forces in coordination with the allies in the hope of inflicting loses that the besieging forces cannot sustain (undermining their ability to achieve their strategic goals).

Morale - It is possible that a limited engagement could affect your adversary's morale more than yours. (remember that soldiers die, but armies route; the goal of military conflict is not to kill the enemy, but to reduce their ability to achieve their strategic goals, frequently by reducing their morale). For example, if you believe you can humiliate or defeat critical individuals on the opposing side, it may make sense to take losses in order to inflict greater losses.

To escape - It may make sense to leave your castle, fight a limited engagement and then ride to relieve another siege; you'll take some losses, but less than if both sieges conclude successfully.

As a final example, if your goal is to take the throne, and the heir you're supporting is bottled up in a castle, it doesn't make a difference if the men in your castle are worth 20, or 200, or 20000, so long as that heir is bottled up in the castle, you've already lost. Your strategic goals require mobility.

"one man in a castle is worth 20 men outside it". is a principle. Modelling any form of conflict with a single principle is foolish. Situations don't rise to military conflict if they can be resolved simply; they are, almost by definition, wicked, complex, difficult problems that involve multiple competing principles.

In the general case, the principle, "Achieve the strategic goals" dominates the principle "one man in a castle is worth 20 men outside it".

Improve this answer
2
  • not always true. A defender army can hope that a siege will end by itself, due to starvation, disease, or increasing upkeep of the invader army. Don't underestimate the last two factors, even when foraging is possible. Or at last that a sequence of sieges will weaken the invaders enough. It is not as sure as kicking their ass, but a smaller country may not have the last option. Deterrence for a smaller country even today is making killing you costlier for the big guy
    – Luiz
    Commented Feb 25, 2022 at 18:51
  • 1
    Everything you say is correct. The topic is broad and I've only offered a tiny sample. Full coverage would be book length and would far exceed my skills
    – MCW ♦
    Commented Feb 25, 2022 at 20:03
5

If you, as the defender, do not go out to drive the attacker out of your land, then they get to plunder it. They can take your crops, kill your people, set fire to buildings, and cause general devastation.

See what happened to Hungary in the aftermath of the First Mongol Invasion of Hungary.

The effects of the Mongol invasion were tremendous in the Kingdom of Hungary. The worst damage was incurred in the plains regions, where 50-80% of settlements were destroyed. The combination of massacres perpetrated by the Mongols, the famines induced by their foraging, and the simultaneous devastation of the countryside by the fleeing Cumans resulted in an estimated loss of 15–25% of Hungary's population, some 300,000–500,000 people in total. The only places that held in the face of Mongol assaults were approximately eighty fortified places, including all of the few stone castles in the kingdom.

The Mongols didn't destroy the Kingdom of Hungary, but they definitely caused a great deal of damage, in turn because the Hungarian forces could not beat the Mongols in open battle.

Improve this answer
6
  • 2
    Likewise the English during the Hundred Years' War -- they would do regular expeditions into France to destroy everything in their way. The French had the option of coming out and fighting or watching their countryside slowly become desolate.
    – Mark Olson
    Commented Feb 25, 2022 at 2:15
  • 1
    I see. Is this the only reason, though?
    – user110391
    Commented Feb 25, 2022 at 2:18
  • 1
    @user110391 With a so broad period of time, there are many reasons: one army could come to help a sieged place (Siege of Acre) and then it became an open battlefield (and sometimes this was an ambush, like the Battle of Hattin), or an army could be attacking the fleeing enemy (Battle of Crécy) or the supply lines/reinforcements (Battle of Wrocław), or even the defending army could be so big it didn't fit into a fortress (most castles could hold less than 200 soldiers) and the battle happened in the open (Battle of Navas de Tolosa)
    – Carlos Martin
    Commented Feb 25, 2022 at 5:35
  • It is actually somewhat misleading: the Mongols were beaten in Hungary the second time by building stone fortifications (from strategic point of view), not by meeting the enemy on the field. If the Hungarians had western European style stone fortresses during the first invasion, most probably the Mongols had much less chance.
    – Greg
    Commented Feb 25, 2022 at 15:46
  • @Greg my understanding is, the second time the Mongols were beaten in battle and scorched earth tactics.
    – Allure
    Commented Feb 26, 2022 at 1:02

Not the answer you're looking for? Browse other questions tagged or ask your own question.