Koreans are the best civ
They have the best seige onagers.

in koreans, its not easy to survive untill castle age, since economy may be slow. Hres a few tips on defence:

Dont bother with sowrdsmen make onl a few pike men handy.
Skrimishers also recommended to defend your war wagons and onagers from calvary.
Keep a miner at stone in dark age.

don't start pumping out soldiers, make small squares of stone gates for your powerful but helpless onagers to hide in, in case of a raiding party of early calvary.

IN black forest, koreans are killers.

Wall up with double sets of walls (best if you have an ally)

Keep advancing upgrades till castle age, make only small groups of spears and skrimishers handy.

Then, start pumping out those war wagons, make about ten or more.

Make also onagers( advancement always recommended.

If u feel strong enough, send your armada foward, with wagons on the front.

keep a few villigers with them, so when things get risky with fighting calvary, you can quickally wall up. Save your onagers! They worth more than wagons, thus they are slow and helpless.

You can laugh as the enemy cavary tries to fight the wagons as the onagers shower fire at them saftly behind the instant walls. when they've gone, make a gate and let the onagers out.

I usually only use towers, walls, wagons, and onagers for sucess in BLACK FORESt.

Re member, koreans have an advantage mining stone.