After years of waning influence, Russia and Iran made a dramatic comeback in the Middle East in 2015 as they threw their support behind Syria’s embattled President Bashar al-Assad.

A decades-long backer of the Syrian regime, Moscow dramatically raised the stakes this year by deploying its air force to bomb rebels fighting Assad’s army.

And after years of isolation and crippling sanctions, Tehran returned as a regional power with a seat at Syria’s peace talks, denoting growing international legitimacy.

But analysts question whether Russia and Iran’s investments will ultimately earn them leading roles in the region, or if they will get bogged down in the Middle East quagmire.

“The resurgence of Iran and Russia is obvious, and their interventionism is increasingly unabashed,” said Karim Bitar, head of research at the Institute for International and Strategic Affairs.

“They are looking to fill the void left by the American retreat” from the region, he added.

This interventionist streak is most prominent in Syria, where the nearly five-year-old conflict has worn down government troops.

After several years of providing financial aid and military advisers, Moscow launched an air war in support of Assad in September.

The strikes have targeted a patchwork of armed forces hostile to the regime, ranging from U.S.-backed rebels to militant groups including ISIS.

‘The West cheated us’
With the collapse of the Soviet Union in 1991, Moscow lost its influence in the Middle East — where it had invested time, energy and financial resources for years — seemingly overnight.

In May 1994, it watched powerless as the Soviet-backed Democratic Republic of Yemen buckled under pressure from the Saudi-allied north.

Less than a decade later, Russia’s influence in Iraq dimmed with the ousting and death of Saddam Hussein following the U.S.-led invasion.

History seemed to repeat itself in October 2011 with the U.N.-sanctioned military campaign in Libya against Russia ally Muammar Qaddafi.

“The West cheated us. We will never forgive them for unilaterally using the U.N. resolution to take over Libya. Never will we let them take over Syria,” a high-ranking Russian diplomat in Damascus told AFP.

Syria is Moscow’s last foothold in the Middle East, and its loss would reduce Russia to a second-rate power.