Experts said Putin wanted to avoid the move, but also wanted to bolster his military.
The move could weaken support for Putin's regime as Russians are exposed to the reality of the war.
The Russian president has found his forces short on manpower while Ukraine, on the other hand, ordered a full military mobilization within days of the invasion in February.
"He's a master procrastinator," Michael Kofman, a military analyst of Russia studies at the Center for Naval Analyses told Puck's Julie Ioffe this week.
Experts told Insider it could take weeks or months for Russia's partial mobilization to bear fruit, as the reservists need to be trained, equipped, and deployed.