My brother's keeper

I've had no luck with any defensive strategy, only early offensive.
The only way I've had any success was to take out the AI town in south corner asap and build up there.

 

Sure. Basically the AI enemy has 4 towns, 1 in each corner of the map and you start in the middle.
What worked for me was to spearmen rush the bottom corner AI town and eliminate it.

Early game it's only defended with a few cav. Kill these cav, then destroy the AI's TC and the villagers there. Make sure you stop them building any military buildings.

Once that town is gone build small walls either side next to their walls and get your 2nd TC built somewhere in the bottom corner. You then have a good market line to your centre start area.

Build up and get to age 4 asap and then make plenty of anti siege - cav usually.
You should then be able to hold out for the duration.

Good luck & pm me in game if you want to do a co-op run.