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I've mentioned this somewhere before, so I'll repeat it:
For the Alliance, you don't need to come up with any sophisticated tactics; the strategy is as simple as pie.
Forget about Anthony; take the specialist in crossbowmen who reduces the armor penetration of his units' bolts. Max out his Tactics (2 levels) and Ranged Attack (2 levels); the rest depends on the situation, but I would recommend investing in Morale, Logistics, and Pathfinding. He should be around level 10 (immediately leveled up on the day of purchase with the help of a mentor). With these cheat-like 75% and some exponential growth in the required experience per level, this skill is a must-have, especially in the campaign. Then, take Defenders, Healers, Riders, Luminaries, and Griffins, and gradually eliminate everyone. Once you've established yourself in a castle, defeating attackers becomes no problem at all; troops are only spent during assaults on their fortifications.
All battles are identical: crossbowmen huddle in a corner and methodically and patiently eliminate everyone (under no circumstances should you let anyone even touch them – their damage increases with each new attack until they are hit in melee combat – the second skill in Ranged Attack).
The only thing to keep in mind is that, even though you're carrying all types of available troops, you shouldn't deploy them all in battle. Griffins should only be used in cases where the assault is expected to be very long. Then, Griffins and Healers will be targeted first, and the crossbowmen won't be touched at all.