To call an ally into war, you must now spend "Favors" earned through years of mutual protection, or promise them a share of the spoils.
They are notoriously difficult to control. Their story is one of dual identity: they are your most loyal defenders against the "heathen" hordes, yet they are always one perceived slight away from declaring their own independent "Sich" and turning their blades against their former masters. Diplomatic Web Expansion - Europa Universalis 4: The Cossacks ...
The "story" is most vivid in the borderlands of the East. The emerge as a unique military caste—independent, fierce, and vital for defense. To call an ally into war, you must
The story of the expansion for Europa Universalis IV centers on the shifting power dynamics of the steppes and the internal struggle for control between a monarch and their subjects. It captures the era when the Great Horde began to fracture and the rising powers of Eastern Europe—most notably Muscovy and Poland-Lithuania—sought to tame the wild frontiers. The Rise of the Estate Diplomatic Web The "story" is most vivid in
Give them too much power, and they may demand more than you can give, leading to a "Coup" or internal strife that can tear a kingdom apart from within. Guardians of the Frontier