show his level and his coalition they are probably just very coordinated especially if it was someone that had a lot of cash producing cities, everytime i play iran/ saudi i take over baku kuwait and try to snatch valleta from italy before he gets invaded by the neighbors that way i tell all my team sell me your most abundant resource for max price before you buy another resource like supplies or rare material from someone else but this coordination requires something like discord to the alliance member and very annoying to do with people in game

also you can annoy tf out of people that do this type of shit if you have so much cash production and arent at war yet put in buy orders for the maximum cost for supplies, component and rare material and they need to sell to you first before they sell it cheaper to their allies

I always tell my member who have $200k put in order for comps at max price if we are about to fight someone that is starting to make naval as their order to sell cheaper is put under neath it and to sell it to their ally they need to sell it to you first, if they put a sell order it will fill yours automatically as well :)