please explain

[Unregistered]

I don't understand the meaning of the last part of the second sentece. Please explain what does "drafted into the Czarist army" mean here. Thank you.

Mark Rothko, one of the most greatest painters of the twentieth century, was born in Daugavpils, Latvia in 1903. His father emigrated to the United States, afraid that his sons would be drafted into the Czarist army

[Anglika]

At that time young men in Russia and its provinces were required to join the army - they were drafted into the armed forces. Also at that time, the head of state in Russia was the Czar/Tsar.