There are 4 winners in the US withdrawal from Syria — and they're all US adversaries

• President Donald Trump's sudden decision to pull US troops out of Syria risks advancing the interests of America's adversaries, according to lawmakers and foreign-policy observers.
• While leaving America's allies high and dry, the move could hand Syria over to the Syrian regime, Russia, and Iran.
• Withdrawing US troops from Syria may also take the pressure off of ISIS at a critical point in the fight to eliminate the terrorist organization.

The US has begun withdrawing American troops from Syria, a decision President Donald Trump made in response to the fall of the physical ISIS caliphate.

"We have won against ISIS," Trump said in a video message Wednesday. "We've beaten them, and we've beaten them badly. We've taken back the land. And, now it's time for our troops to come back home."

Critics argue that withdrawing from Syria at this time risks advancing the interests of America's adversaries. "The big winners of this decision are ISIS, Iran, Russia and Assad," South Carolina Sen. Lindsey Graham told The Washington Post after calling the president's decision an "Obama-like mistake."

White House and Pentagon officials have been unable to offer clarity on the situation, with questions about timelines, expectations, and the mission going forward remaining largely unanswered.

Read more:Trump just radically upended US Syria policy despite repeated warnings that doing so could be disastrous

There are serious concerns among lawmakers and foreign policy observers that the president's decision will basically hand Syria and its future over to the Syrian regime-Russia-Iran axis, leaving our allies vulnerable and the stability of the region in jeopardy.

Here are the groups that stand to benefit from the US' move:

SEE ALSO: Trump just radically upended US Syria policy despite repeated warnings that doing so could be disastrous

Russia

Moscow celebrated Wednesday's surprise news that the US plans to leave Syria "as quickly as possible." The Russian Foreign Ministry, according to Russian media outlet Tass, said"hope emerges," arguing that "once Americans were there, there was no such hope."

The Russian military has been active in Syria since 2015. Without the US military standing in its way, Russia will be able to significantly expand its influence.

Iran

While the primary mission of the US military in Syria has been the "enduring defeat of ISIS," it has also been to counter troubling Iranian activities in the region.

Secretary of State Mike Pompeo said in October that a US objective was "the removal of all Iranian and Iranian-backed forces from Syria." One month earlier, White House national security adviser John Bolton said US troops would not "leave as long as Iranian troops are outside Iranian borders and that includes Iranian proxies and militias."

The US military presence in Iran has disrupted Iranian activities, but withdrawing US troops from Syria will permit Iran to more easily pursue its interests.

Syrian regime

The US has repeatedly expressed dissatisfaction with Syrian President Bashar Assad, with some observers assessing that he might eventually be removed from power. The US military placed at least limited restraints on the Syrian military.

Pulling US troops out of Syria risks emboldening Assad, as he feels more secure, leaving his enemies — which have fought alongside American forces — more vulnerable. With the threat posed by ISIS degraded, Assad could, with the support of his Russian and Iranian allies, focus his efforts on retaking territory lost in the civil war.

And, as the US will no longer have a military presence in country, the Syrian regime, in coordination with Moscow and Tehran, will be free to dictate the post-war outcome.