Well, according to page 184 of the D20 rpg main rulebook for SST...
The Mi counted 4,855,122 soldiers at the time of the pluto campaign,
headed by the "sky marshal in chief" and his 5 advisory generals, organised in 28 armies.
Each army is headed by a skymarshal.
4 divisions form an army, each division is headed by a General, and is called Corps if it includes fleet assets.
4 Brigades, headed by Colonels, form a Division
4 Regiments, headed by Lieutnant Colonels, form a Brigade
4 Battailons, headed by Majors, form a Regiment
4 Companies, headed by Captain, form a Battailon
4 Platoons, headed by a Lieutnant and a Sergeant Major each, form a Company
4 Squads, each 10 men big, lead by a Sergeant and a Corporal each, form a Platoon.