“Why doesn’t he use fully trained and active duty troops? “
Employment in Russia is bad. This represents 150,000 jobs. It takes people off the streets and puts them under state control. It trains people for the regular army. It does not affect Russia’s other military concerns or their ability to fully prosecute a war elsewhere. Other than the possibility of mass casualties this deployment has few downsides. Putin has plenty of political capital to spend at home.
Good analysis.