Alright, i've never done this before but I thought just what could be good about the Korean hwacha? I thought about it and now I believe that the best way to use it is not to eliminate enemy stacks - thats just not what it is for. That is thinking inside the box. Instead, you could make 3 squadrons of 10 infantry, 15 artillery and 10 hwacha and placed each squadron on mountains next to enemy cities or across a river from a city. Every turn, they might send cavalry to attack these squadrons but from experience I know that if your stack is big enough with lots of infantry they sometimes hesitate to attack it. So your squadrons are next to these enemy metros. Now you wake your artillery and blast all 15 shots into the city so all the defenders in that city are redlined. Now wake your hwacha and do em away. Now the cities are empty but DO NOT send in a unit to capture it. Let the turn finish and the enemy will send in extra units to defend that city and possibly even draft or whip that city for more units. You do this procedure again and again every single turn until they run out of units and population points. It would work very well because they hesitate to attack your stack and because they always send extra units to fill in those empty cities. Pretty soon, they will be defenseless and unable to do any research nevermind get to discover Flight because they are spending on military production. When it looks like they've had enough, out come your cavalry and sweep em off the face of the planet.