There
are many factors that are involved when an era transitions to the next. It
usually involves a large change in political, social, and economic factors. Examples
are colonization, economic progress or downfall, or changes in the government. Each
era has a corresponding theme that is heavily influenced by important events
that have happened within it. Examples are the age of enlightenment, industrial
revolution and the renaissance.
"Irredentism is any political or popular movement that seeks to claim/reclaim and occupy a land that the movement's members consider to be a "lost" territory from their nation's past. Wikipedia"
