With which country did otto von bismarck purposely start a war in 1866 to gain control of german-speaking states?

Otto von Bismarck had started unified Germany by uniting the three factions of the country in order to fight against foreign rule. Bismarck had first invaded Denmark in 1866. Then he  attacked Austria, as he gathered the Germany under the rule of the Kingdom of Prussia

i think it should be slowed colonial western march

the decreasing neutrality of the u. s. in world war i

hope this : )