Well he didn't attack us so I attacked, our stack is destroyed. Here's the combat
Hwacha vs longbow, 1.8% LOSS
Hwacha vs longbow, 1.4% LOSS (at that point I decided, which was a poor judgment in hindsight, that collateral was better than city attack, because I wanted to collateral the knights hard so the other units could have a chance, all it did was keep the longbows alive for much longer)
Hwacha vs longbow 1.4% LOSS
Hwacha vs longbow 1.4% LOSS
Hwacha vs longbow 1.4% LOSS
Hwacha vs knight 3.1% LOSS
Hwacha vs knight 3.1% LOSS
Hwacha vs knight 3.1% LOSS
Hwacha vs knights 3.1% LOSS
Hwacha vs longbow 5.3% LOSS
Hwacha vs longbow 5.3% LOSS
Hwacha vs knight 4.3% LOSS
Hwacha vs knight 4.3% LOSS
Hwacha vs knight 9.9% LOSS
Knight vs Pike 21.7% LOSS
Knight vs Pike 22.1% LOSS (1 hit inflicted...)
WE vs Pike 9.3% LOSS
WE vs Pike 17.4% LOSS (1 hit also)
HA vs Pike 5.3% LOSS (I wanted to keep the WE for after the pikes, so they could attack the knights, this first HA almost killed its opponent so I did it a second time)
HA vs Pike 4.3% LOSS (used flanking 1 on him)
WE vs Pike 21.1% LOSS (1 hit again)
WE-Mace 33.4% LOSS
WE vs Longbow 35.9% WIN (finally, 8HP left)
Sword vs Axe 40% LOSS
Sword vs knight 48% LOSS
HA vs knight 2.5% LOSS
HA vs knight 3% LOSS
HA vs Knight 7.9% LOSS
HA vs knight 7.9% LOSS (that's when I realized the pikes had odds, silly me)
Pike vs Longbow 41.2% LOSS (NO HITS INFLICTED)
Pike vs Longbow 41.2% WIN (to compensate I guess)
Pike vs Longbow 58.2% LOSS (1 hit inflicted)
Spear vs Mace 11.1% LOSS
Pike vs sword 45.3% LOSS
HA vs knight 9% LOSS
HA vs knight 9.1% LOSS
HA vs knight 7.5% LOSS
HA vs WE 10.2% WIN (50HP left, thanks RNG it's super useful !)
HA vs knight 5% LOSS
HA vs knight 17.5% LOSS
Note that the HAs all had 20 or 30% odds of retreating (I gave some of them flanking) and NOT ONE retreated. I expected to do some damage to his stack with this attack, delay his counterattack for a few turns. Now here's the state of things, with most of his units awaiting a promotion I suppose (some of them at least). I didn't mention all the hwachas that did absolutely no damage at low odds because well, the odds were low on them anyway. I'm certain that what I did was not optimal, you're much better when it comes to military, I probably gave some units the wrong promos and stuff.
He doesn't even have a unit in some of his cities...
Good news (I guess) is that I captured the barb city in the north, now in 3 turns of rebellion. The main problem with our attack was the lack of pikes and knights, with more pikes we'd have destroyed most of his 1-movers and with more knights we'd have gotten some of his C3 knights. Also both sides got a GG in the process, ours spawned at MCG (convenient) and I put him on a pike with healer promos (all the way to healer 3). He's in GJ's borders already. Next turn I suppose we fall back.