Actually I did have a battle like that recently. I was playing Extended Realism 4.0 as Bactria. You start out with very little, and can only recruit decent units in one settlement. I decided I was going to expand into India before taking on the juggernaut that the Seleucids are. So I took a few settlements, actually starting having a surplus of cash at the end of each turn, so life was good. But I still only had enough cash for one army, which was campaigning in India.
Then the Seleucids decided it was time for me to come under their control again. They attacked Bactria (the settlement, my capital, and my only recruiting grounds where decent troops could be raised) with a full stack of Pezoi, three generals, archers and some Theurophori (sp). I myself had a large number of Theurophori and only two archers, and one new general at the helm.
Now the Seleucids were smart in that they made sapping points, as well as ladders, towers and one ram. I thought I was genuinely screwed. I couldn't do the cheap method of letting them be peppered by towers because they would all rush my defenses as soon as the walls were down, and I still had to play a a decent amount of units on the walls because wall fighting in RTR is amazingly taxing on soldiers, and unexpected wins happen.
I then did the only thing I could do to realistically win, at a reasonable cost to lives on my end. I put the archers on the wall, and managed to set light to one tower, and then had them pepper anyone else who came into range. I put one unit of Theurophori on the wall away from the action, so that when the Seleucids took the wall, I could quickly reclaim the towers and gate. The rest of my units were at the square, where I knew they would fight to the last (as game mechanics make it so). So I did my strategy, which worked like a charm, and as their being peppered in the streets by my towers, my men throw their javelins and await the attack.
Luckily their entire army was fighting the majority of my army in the center itself, and the Pezoi broke formation and fought with their swords, giving my guys an advantage. The slaughter of both sides then ensued, with my guys eventually outnumbering theirs, as their men ran away from either lack of stomach, depleted numbers, or the disheartening even of seeing their commander slain. I did almost lose though, as their Pezoi came back from routing but in formation this time, giving my men a very hard time. I was only saved because I had forgotten the unit of Theuropori on the walls, and then brought them into the fray, breaking their formation.
I did win in the end, but I had very little to defend myself with in my home area. I had my army being rushed back to retake Bactria if need be, but after the victory they went back to taking India. I would later lose Bactria to the Seleucids, but they had two stacks and I myself had only an archer, a general and a unit of Bactrian infantry. It was bad for my economy in the short term, as I would then gain a debt of roughly 6,000 per turn, for 7 turns as my army in India made a hasty peace and beat it Alexandria on the Oxus. I had my other nearby towns able to recruit troops of reasonable strength by then though, so I did not lose any more towns, but if the Seleucids had capitalized on their victory, it would have been much worse.
I am the Carthaginian who became an angel, and surrendered his wings for a life on the sea of battle.
My magic screen is constantly bombarded with nubile young things eager to please these old eyes. This truly is a wonderful period in which to exist! - Terikel the Deflowerer