What political factors lead to unity within an empire?

The political factors that lead to unite an empire or within the empire might be the following;

-       Government stability, the leadership in the government, the corruption levels and the stability of neighbors.

These factors helps the unity within the empire as it makes the empire more stronger together with the people surrounding it as it provides equality and goodness to mankind.

they kept back from the wars and didn't want any action meaning wars.

lincoln declared that slavery should not be allowed to spread into the new states, and of course this angered the south at the time.