The Executive Branch
Mypay is a service provided to military service members that allows them to get paid and see their financial services online. The government, who is the employer, finances the transaction.
Enforced military service ordered by the government is called conscription or (colloquially) "the draft."
Draft, conscription, or compulsory service.
A civil service job is a job that is usually in a government sector. This doesn't include the military and military jobs.
Draft men to serve in the military
Feudalism is the form of government and the nobility were required to give so many days a month to the king for military training/service.
The US Marines are a military branch of service. There is a RECORD of every person serving in the US military.
who work for the government in non-military positions
Required men to register with the govt. for a draft, in order to be randomly selected for military service. May, 1917
Invented
Civil service is commonly used to define any government employee that isn't in the military. It is sometimes used to refer to a branch of government of hired professionals.
The Selective Service Act, although the definition you give of it is a bit misleading.