"As of the last yearly census, roughly 20% of the population is serving in active military roles with about half the population, including the 20%, acting as reserves. These numbers are derived from conscription policies which eligible males and females have to serve a set amount of time in the military. It should be noted the numbers include non-combat roles like military police, guardsmen, medical personnel, hospitality corps, etc."

20% active military, with 30 more percent acting as reserve, half the population is linked to the army, along this you have an emperor with 100% authority on everything. The way my people see it, if one night said emperor decides to go to war, then it's nation needs 0 buildup and 0 preparation to launch an invasion the very next morning.