Why did the number of nuclear weapons crash during the 1990s?

Why is it useful for historians to base certain studies on the analysis of historical themes

As the tide of the seven years’ war (french and indian war) turned in britain’s favor, the iroquois

By choosing to resupply fort sumter, abraham lincoln risked a. abandonment of the fort by union soldiers. b. abandonment of the fort by confederate soldiers. c. the appearance of giving in to confederate secession. d. armed conflict with southern soldiers.