My solution was /is as I do this land for fun is contained in the following.
If you build fast enough then everything can work , if not then you wil be able to continue.
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First off... Start tobuild a wonder (I prefer the siren) near your worship site so it gets 100% productivity. You won,t be able to use it but the influence area is important.
Second...Expand your influence to cover where the volcano will erupt . If done soon enough the volcano will not be fired.
3. Build a secondary wall outside the given wall , where the attacks will take place, once the siren is built you can do this.
4. Gather some of the large rocks and put them handy....you know where the attacks are to come from.
5. The Great battle ......Archers on walls Swords ready to plug holes.
6. The enemy have the disadvantage 2 walls to clear in your influence and ...as a good god to protect your people you can drop the rocks on the enemy creature and catapults first then help mop up the troops without casting a miracle.
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I hope this clears your problem. Sometimes it works 100%
Others 99% of the time you can recover and go on to win the game even if you don't get it right