Why did secretary of defense say that the United States needs Russia as an adversary?

How did the enlightenment change attitudes about existing political systems

The largest lake in south america is lake titicaca?

Historians are concerned with the accuracy of their writings and readings but are also aware of the inability of authors to know every angle of every story biases, perspectives, beliefs, and a variety of other differences history being told by one person at a time no one being totally accurate, as hard as we try really need on this, and you^^