How do I attack a strongly-defended position?

[Tuidjy]

If the army is not under a great many domes, hit it with everything you have.
You can tell by looking at your replay. The domes should appear in the upper
right corner. If there are only a few domes, hit the province with twenty
voices of Aspu (enlist other players to help) and then let loose with Flames
from the Sky, Beconning, Murderous Winter, yada, yada, yada... Do not forget to
cast the voices on the turn you send the damage dealers, as well.

If there are more than a few domes... Well, the odds are against you.

As for the attack, yes, you will have to survive the first turn. Against a good
Arco, it's a nightmare. He has most of the elements, and some meteors to toss
on top of that. You need decoys. Tartarians are great for that. But frankly,
you are attacking - unless you are much stronger, you are supposed to lose.
But if you survive the first turn, use all the battlefield enchantments you have,
and watch his human mages drop off like flies.

[Twan]

The battle was only won by my indie mages with earth/air, allowing me to cast several rain of stones in round one. If you have the gem income and forge capacity to give a good protection to 30 or so mages (and add your tartarians etc) you have chances to defeat my army I think (I see some tactics I can't counter, but I won't say more of course).

[NTJedi]

IndyPendant... in my opinion we need more information for what units, mages, thugs and SCs are expected to be in the province when you attack. Also any blessings and the type of sacred units for the attacker and defender.

This late in the game it's unlikely the ususal Arco troops are the only ones defending.

[Zeldor]

NTJedi:

In battles like that troops are not so super important. If he cannot survive one turn then Arco can as well have just 1000 militia around mages