Late game. How do we win a game playing Japanese and Britons vs Koreans and Spanish?

As above, this just happened in a random game. Asked my teammate a possible strategy to counter their units but we found none.

The spanish were making bombard towers + paladins, the koreans wagons + siege onagers.

What we were supposed to do? Any idea? For my side, I tried to use my fastest Trebuchet to rake down their towers and to use halberdiers vs his waves of paladins but we weren't able to hold much because of the koreans