Russia
The Russian military is divided into the Ground Forces, Navy, and Air Force. There are also three independent arms of service: Strategic Missile Troops, Aerospace Defence Forces, and the Airborne Troops. , the military comprised over 1 million active duty personnel, the fifth largest in the world. Additionally, there are over 2.5 million reservists, with the total number of reserve troops possibly being as high as 20 million. It is mandatory for all male citizens aged 18–27 to be drafted for a year of service in Armed Forces.
Cossacks
By the end of the 19th century, the Cossack communities enjoyed a privileged tax-free status in the Russian Empire, although they had a 20-year military service commitment (this was reduced to 18 years from 1909). They were on active duty for five years, but could fulfill their remaining obligation with the reserves. In the beginning of the 20th century, the Russian Cossacks counted 4.5 million. They were organized as independent regional hosts, each comprising a number of regiments.