What development was most important in allowing some people to specialize in activities other than food production?

What lands were added to the russian empire under ivan iv, peter the great, and catherine the great?

What was president nixon’s approach of using tension between us and other nations

Even though both ww1 and ww2 were in many ways the same conflict with basically the same countries facing off against each other, the way each war started was significantly different. the question is how what were the differences on how they started