My mistake as at the fork on turn 3 you can switch and have your commander go left while the rest of your armies goes to the right and win Center SW on turn 6. The West AI underestimates your leader's attacking resources and should defend Center SW and Center SE equally.
Quoting Member Kicorse from a previous post 04/27/2018:
In fairness, it is correct to say that "it is impossible unless the AI makes a really stupid mistake". The initial position is completely won for the AI. The thing is, the AI is guaranteed to make such a mistake, because it prioritizes expanding over attacking/defending and it doesn't understand delays. You just need to exploit that.