It's a branch of sociology that looks at how societies develop through history. The idea of sociology is to deconstruct how things such as wars and climate lead to social structure and hierarchy.

Historical sociology is looking at how societies change through history. For example:


One could look at Venice which arose to become a very powerful city state. It's trading abilities and prowess made it very wealthy and dominant but lost this position of power when Portugal became the main trading center for Western Europe to work with the East.