Can Putin legitimately declare "mission accomplished" in Syria?

If legitimate, this strategy seems the opposite of American [Western] engagements where the military ‘support’ drags on for years or decades.

Mr. Putin decided the withdrawal was justified by the “overall completion” of Moscow’s military mission in Syria. “I consider the mission set for the Defense Ministry and the armed forces on the whole has been accomplished,” he said at a meeting at the Kremlin.

The news on Monday, relayed personally to the Syrian president, Bashar al-Assad, in a telephone call from Putin, followed a meeting in the Kremlin with the Russian defence and foreign ministers.