The XL mod

[Banquo's Ghost]

I didn't look but it was right at the start of the game ...

Therein lies your problem. I's always a good idea to scout the enemy before hand. Particularly in XL, there are often new units (not saying these were) which surprise you. Even basic units can turn you over when unprepared - I remember getting whupped thoroughly by a bunch of woodsmen that I had dismissed as filthy and cowardly peasants. (The kind of over-confident mistake too many generals have made in history).

I love surprises and challenge, so I love the XL mod, but even in vanilla it's wise to know who and what you're up against before battle.

[Odin]

The XL mod does 2 things that make it more challenging then vanilla.

1. Land is power: This concept increases the land income values and decreases the trade values. Since your fairly new to MTW in vanilla you can set up a mamoth trading empire with lots of income. The AI struggled with this and could never compete economically with the human player. Now it at least can develop land and get a similar income.

2. Better units: The AI in XL dosent seem to employ crap units as much, it seems to spend its money and get better quality units. While certainly not insurmontable for a human, its a harder fight for sure.

Points 1-2 are stated by ajaxfetish when he talks about the AI ability to manage its economy. I agree with him and I believe its the the increased land values that make the AI have more income, build upgraded buildings and therefore produce more units.

Most mods find away to do this, I just happen to play XL exclusively because it does everything well enough for my taste. I have played it for sometime and dont think I will ever go back to vanilla. The additional music scores are nice as well, They have grown on me. So yes I like it, but MTW has been around so long that there are 4-5 very good well developed mods for the game, try them all and find one you like.

[Ciaran]

Keep in mind, on the average the XL mod increases Morale of all units by two, that means units will stay in battle much longer than in vanilla. This little tweak alone has a huge impact on how the battles play and it takes a while to get the feeling for the battles back. I found it frustrating as well when I started, but after a while you´ll get the hang on it.
A second issue, XL has removed peasants. That sounds not big, but it has a definite impact. There is a difference of whether you´re attacked with sixteen peasants or sixteen Urban Militias.

That´s the battle part, the various strategic changes have been mentioned already.