Russia has 1 year mandatory service for all males, with scads of exceptions. Maybe not unlimited, but plenty of poor bastards who couldn’t get into a university or hit one of the other exemptions. Per the usual, the elites have a choice, not the little people.
That’s true that everyone serves, but conscripts aren’t sent to war. They get basic training, work for a year (mostly in logistical type work), then go home. It’s sort of a rite of passage in Russia. Just about everyone sent to an active war zone these days are volunteers. Also, in years past, the wealthy could buy a fake or official but corrupt “army ticket”, (which is essentially your proof of service and discharge, without which you pretty much can’t get a job), but after they busted a giant operation that was doing these “left” papers, it’s pretty tough to get around it. Even people that do advanced degrees often have to go after they graduate.