Request for assistance

[Renegade 13]

Hey, I have a few questions about DomII. First off, I've owned it and played it off and on for about a year and a half or so, but have never really aquired a whole lot of skill in the process Anyways, if anyone can help with my questions, please feel free to do so

Recently I've been playing a few games with lots of players and a large map. Usually roughly 10-12 players ("Normal" AI's) plus myself. Recently, I've played as Man and Ulm, yet the same thing has happened to me both times. I start out well, conquer the independents in the immediate area without trouble, and usually wipe out the closest AI as quickly as possible. Both times I've ended up with roughly 20 provinces, a few moderately sized armies, and all provinces explored for magical sites using the Acashic Record spell. It's notable to mention that I'm not skilled in the use of magic, and usually relegate it to the back burner, focussing on conventional armies.

My armies are usually mixes of fast, heavy troops and supporting missile troops. My mix is usually a ratio of about 2:1, missiles to heavy troops. Often archers in the back and the toughest cavalry I can recruit up front. With this mix, I wipe the floor with the AI in almost all battles, but can have trouble with large (100+) armies of weaker AI troops. So here comes my problem...

I always seem to hit an AI empire that has absolutely massive armies, and lots of them. This is usually around turn 40-50. I expand as much as I can, recruit what forces I can, but eventually they declare war on me and wipe me out without thinking twice about it. I just don't understand it; I'm recruiting as much as possible, using quality troops, yet the AI seems to be able to annihilate me with 6 or more 80+ troop armies. So, essentially, my question is how to avoid this, how to avoid the pitfall at this point in the game.

Pretty much, is there a detailed strategy guide for this stage of the game, something to teach me what I'm obviously missing?

Thanks!