What are good strategies for fighting enemy forces that are far, far larger than your own? I recall that in medieval war, pitched battle was rare, and wars usually lasted until either the attacker achieved something resembling their objective, or the defender managed to... persuade them that they were wrong about achieving said objective being worth the losses. So the goal, then, is not necessarily to charge out and slaughter the enemy, but rather to make continuing to attack look as unattractive as possible to them. It might also be helpful to politic the enemy commanders into hating each other too much to work together, but more on that in a minute.
Allow me to provide some background to my specific case. I'm really asking this so I can offer tactical advice to one of my players, as his character concept is sort of a strategic genius/great leader type, but he's not actually very familiar with medieval strategy (modern strategy, he's rather experienced with, but that's a whole new ball game). Basically, he's a landed noble who's serving as the officer of a greater baron, and they're in some very hot water. In recent story events, the character (with help from a magus who is likely drinking tea and getting ready to enjoy the war at this point, because he only helped the noble character to watch the following conflict unfold) managed to acquire for the Greater Baron a golem that many other larger and more powerful nobles were vying to get. That yielded a bunch of Gratitude, but also a lot of enemies, who aren't willing to give the golem up that easily. So they formed a coalition and have combined their armies into a pretty cataclysmic force. (Based on their knowledge of the golem's abilities, it's not entirely unreasonable to think that whoever figures out how to use the golem could take over a significant chunk of all of Europe, so this amount of effort is far from unjustified.) And the path they're taking to the Greater Baron's city? Straight through the character.
Now, I'm not specifically trying to screw this character over. I figure, this is a coalition that isn't likely to bear its own weight for long, and there are probably ways to deal with the size difference, like chevauchee tactics and guerrilla warfare and, if it comes down to it, digging in for a siege and praying for a miracle (perhaps literally). However, I'm sure we're not thinking of everything, and I want to get some opinions from you guys so I can help him out. What would be the best non-surrender options at this point?