I have read that attackers should outnumber defenders, 20 to 1 or better 50-100 to 1 in sieges in a book about conquest of İstanbul, though I can not find its reference right now. I remember that this book claims that no attacker has even won a battle with lesser numbers without help (treachery) from inside in middle ages and before.

Is there any references about these numbers, or similar numbers about sieges' opposing forces ratio. It is understandable that attackers should outnumber defenders, but how much?

I would like to learn average Average Attacker to Defender Ratio in Middle Ages for sieges with references to journal articles or books.

EDIT: Actually, any reference to respected historian is enough for me. Comments give reference of Sun Tzu but I would like to get number for Middle Ages European if it is possible. But if it does not exists, it seems I would have to accept Sun Tzu Art of War.

  • The usually cited ratio is 10:1, which was taken from the Art of War by Sun Tzu. I'm not really sure what you're asking for here, though. – Semaphore Nov 27 '14 at 12:22
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    Any other ratios from middle ages? – Atilla Ozgur Nov 27 '14 at 12:24
  • @Semaphore I changed my question according to your comments. – Atilla Ozgur Nov 27 '14 at 12:32
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    Are you asking for people to give you a list of sources, or would you like to get some sort of a rule-of-thumb? Both have their problems: any ratios from the Middle Ages will necessarily be estimates, because there were no TOEs back then and civillian population would often help defend a city; any recommendations, on the other hand, will vary wildly depending on the specific circumstances. Sun Tzu is often cited, but his ratio is basically pulled out of his backside. – Mike L. Nov 27 '14 at 14:13
  • @MikeL. I edited question, Middle Ages European if it is possible. – Atilla Ozgur Nov 27 '14 at 14:17

Following and expanding on from Mike L's comment the short answer will be we don't know. Numbers of armies as quoted in works at or close to the time were often (always?) exaggerated, you know our guys only had 10,000 and the bad guys, they had a 100,000 and we still beat them. Camp followers and townsfolk could also get lumped into the count regardless of their combat effectiveness or drain on resources.

The other thing to remember is the main people counting were the heralds. And their job was to note the demise of important people Sir XYZ, Monseigneur EFF, Landsknecht Von D, The Kings Brother/Son/Nephew etc. A small part of the fighting force but well worth a ransom. The bowmen, crossbowmen pike-men, halbadiers and the townsfolk were in their opinion worthless so rarely counted or counted accurately. I mean why bother when no-one cares?

I suspect to get any sort of answer you would need to look very carefully at the information available about the size of armies, remembering that because of logistics most medieval armies could not usually number more than 20,000 except in exceptional circumstances and make your own estimation of the size of the armies and then with more difficulty try to get estimates of the size of towns taking into account no real census data being available and populations fluctuating by season or plague. No doubt here tax and poll records would help but are still open to interpretation.

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