Didn't find any thread discussing the strategy for this achievement. Anyway now that the Qing cores/nation forming are fixed I quickly attempted this.
I used Haixi but others should be easily doable too. I believe in letting AI do the work for me, and the real advantage in Haixi is diplomacy: I allied Korea and vassalized Jianzhou day 1. Now with vassal army I vassalized Korchin and took the required provinces from Yeren.
In the meantime I allied Ming, started war with Oirat. Oirat army cut through Ming like butter but Ming do have a lot of men. So after they fought to exhaustion I took the other required province and also vassalized Buryatia(sp) who is Oirat ally.
Now Ming army is dead, Jianzhou should be diplo annexed and you should be tech 4 while Ming with shit tier emperor is at best 3. I simply set Ming as rival and after alliance dissolve I declared war and man it was too easy with inward perfection and horde super units. Took the provinces and also get vassal Shun.
I used Haixi but others should be easily doable too. I believe in letting AI do the work for me, and the real advantage in Haixi is diplomacy: I allied Korea and vassalized Jianzhou day 1. Now with vassal army I vassalized Korchin and took the required provinces from Yeren.
In the meantime I allied Ming, started war with Oirat. Oirat army cut through Ming like butter but Ming do have a lot of men. So after they fought to exhaustion I took the other required province and also vassalized Buryatia(sp) who is Oirat ally.
Now Ming army is dead, Jianzhou should be diplo annexed and you should be tech 4 while Ming with shit tier emperor is at best 3. I simply set Ming as rival and after alliance dissolve I declared war and man it was too easy with inward perfection and horde super units. Took the provinces and also get vassal Shun.