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.

There were several events that contributed to the fall of the Soviet Union. The most important ones ( with the dates included) are as follows:

December, 1979: Soviet troops invade Afghanistan to help the country's communist government to fight the guerrilla forces.January , 1981: Ronald Reagan becomes U.S. president. During his two terms he implemented a weapons policy that  the Soviet Union economy couldn't afford.March , 1985: Mikhail Gorbachev becomes president of the Soviet Union at 54 years old. He introduces glasnost (meaning openness) and perestroika (menaing reestructuring) in an effort to overcome economic and political problems.  February , 1989: The last Soviet soldier leaves Afghanistan. May , 1990: Boris Yeltsin is elected chairman of the Russian Soviet Federated Socialist Republic. (URSS) December , 1991: After surviving a coup, Mr. Gorbachev resigns as Soviet president, marking an end of the Soviet Union.