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

The correct answer is Austria.

In 1866, the Kingdom of Prussia declared war against the Austrian Empire.

roosevelt believed that in light of the country's recent military successes, it was unnecessary to use force to achieve foreign policy goals, so long as the military could threaten force. this belief, and his strategy of “speaking softly and carrying a big stick,” shaped much of roosevelt's foreign policy.