(CNSNews.com) – Russian President Vladimir Putin, on a surprise visit to Syria Monday, announced the abrupt withdrawal of Russian forces after a deployment that has evidently succeeded in preventing the overthrow of Syrian President Bashar al-Assad.

Russian pilots began returning home immediately, according to the Kremlin.

Visiting the Hmeimim airbase in Latakia province – the hub of Russia’s military operation in Syria – Putin and Russian Defense Minister Sergei Shoigu met with Assad and addressed Russian personnel, thanking and congratulating them on their achievements.

“By helping the people of Syria to maintain their statehood, to fight off attacks by terrorists, you have inflicted a devastating blow to those who have directly, brazenly and openly threatened our country,” he said.

“In just over two years, the Russian armed forces and the Syrian army have defeated the most combat-ready group of international terrorists,” Putin said. “I have decided to redeploy most of the Russian military contingent from the Syrian Arab Republic to Russia.”

Putin launched the airstrikes in Syria on September 30, 2015, in a campaign ostensibly targeting ISIS but seen by the U.S. for much of the time as primarily designed to prop up the Assad regime – by targeting rebel groups other than ISIS, including opposition groups which the West has supported.

Apart from pilots and air force support staff, Russia deployed special forces troops, sailors, reconnaissance and logistic support units, military police, medical personnel, field engineers and advisors.

Russia also used the opportunity to test military capabilities in combat environments, for example launching cruise missiles at targets in Syria from warships in the Caspian Sea – traveling more than 900 miles across Iranian and Iraqi airspace – and also from a submarine stationed in the Mediterranean.

Putin’s unexpected visit to Syria – his first as president – was added onto a scheduled trip to Egypt. Russian media say the president will also go to Turkey for talks with President Recep Tayyip Erdogan about President Trump’s

The order to withdraw Russian forces from Syria comes four days after Shoigu reported to Putin that the country has been completely liberated from ISIS.

The U.S. reserved its judgment, and U.S. Central Command commander Gen. Joseph Votel, speaking in Bahrain on Saturday, cautioned that the claim could be premature, saying pockets of ISIS fighters in Syria probably numbered “well into the hundreds” if not many more.

“The Russians have declared operations over with, it is hard for me to understand how they would reach that conclusion,” the U.S. Army general was quoted as telling reporters.

“We, as the [U.S.-led anti-ISIS] coalition, are still fighting, and we intend to complete the operations that we are undertaking in the middle of the Euphrates valley, and some other areas that will be necessary,” Votel said.

The Centcom commander also expressed concern about the ongoing presence in Syria of Iranian and Hezbollah forces.

Tehran has provided Assad with financial, military and moral support, and its Lebanese Shi’ite proxy Hezbollah has also been deeply involved in the fighting on the side of the regime.

Russia and Assad have frequently emphasized that Russia and Iran are operating in Syria at the request of the Assad regime, unlike the U.S. and its partners, which they charge are violating Syrian sovereignty and international law by carrying out military operations there.

In contrast to the U.S. reaction to the Russian-Syrian-Iranian claim that ISIS is Syria is defeated, the administration welcomed Iraqi Prime Minister Haider al-Abadi’s announcement on Sunday that security forces had recaptured the last areas of that country from the Sunni terrorist movement.

“[W]e offer our sincere congratulations to the Iraqi people and to the brave Iraqi security forces, many of whom lost their lives heroically fighting ISIS,” said State Department spokeswoman Heather Nauert in a statement.

“The Iraqi announcement signals the last remnants of ISIS’s self-proclaimed ‘caliphate’ in Iraq have been erased and the people living in those areas have been freed from ISIS’s brutal control.”