I've completed most of the extreme trail and thought i'd share the first six missions for anyone having difficulty.
I found that slowing the game speed helped.
Buy enough stone and wall yourself in and build square towers and fill with both european,arabian and crossbowmen,place slingers and fire throwers to deal with any troops that get too close,this seems to work best in all the scenarios so far-however,further on you fight and defend like crazy due to the outposts,so i used the 'tactical aid' to destroy those nearest-mission 2 in particular.
the save files are
(2) bird in flight
SPOILER-mission six there is an outpost to the lower right of your keep destroy it first(2)wall of the keep and place three square towers with archers and ballistae,as the caliph uses catapults.