Making allies in the campaign in old AoK?

I remember being able to make allies in the campaign with some factions, like Burgundy in the third Joan of Arc mission or maybe in the first Barbarossa mission. You'd offer them a bunch of resources and turn them into ally in diplomacy and there was a chance they'd become your ally. This can still work in regular games (not campaign) I think.

Am I imagining things or was this possible before?