Moscow has repeatedly hinted it could send some of its most advanced air defense systems to Syria.
ISIS has agreed to surrender its final stronghold south of Damascus, but the Syrian military and allies continue to fight until talks are finalized.
The U.S. gained an ally in Baghdad after overthrowing Saddam Hussein in 2003, but an alliance of Iran, Iraq, Russia and Syria is growing stronger.
Iran is sending officials to Lebanon, Iraq and Syria as tensions mount with Israel, Saudi Arabia and the U.S.
Syria celebrates 72 years of independence from France on April 17, 2018.
Since 2001, the U.S. has been involved in several ongoing overseas conflicts with no clear end in sight.
The world's top two military powers may be on a collision course in Syria.
"The Russians met their match," said CIA Director Mike Pompeo, who has been nominated for secretary of state.
"We hope the Trump administration thinks twice before deciding to attack Syria," the ruling Chinese Communist Party's newspaper said.
Defense Secretary James Mattis is heading to the White House to show President Donald Trump his options for attacking Syria.
Two opposing, multinational alliances are forming as President Donald Trump decides whether or not to attack Syria.
Russian jets are soaring over the waters of the Mediterranean, and Syria has moved new air defenses near Assad's presidential palace.
President Trump could decide whether to attack Syria as soon as "later today," a move that could draw a Russian military response.
A high-ranking defector's testimony details the regime's plan to target foreign journalists to silence independent reporting on the now seven-year-long conflict.
The Syrian military has forced the insurgents of eastern Ghouta to either surrender or leave, but pro-Assad forces expected a fight with ISIS in the south.
The U.S. and Russia have both contributed to the fight against ISIS, but their goals for postwar Syria differ.
Iraq and Syria declared victory over ISIS in late 2017, but the U.S. and Turkey have resisted calls to withdraw their forces.
Syria has been ravaged by a bloody civil war for the past seven years.
Tensions between local and international actors have led to nonstop violence and more than 500,000 deaths, but there are some signs of rehabilitation.
Less than two weeks after Russian President Vladimir Putin showed off advanced weapons, his officials are warning the U.S. against action in Syria.
The shifting dynamics of Syria's seven-year war have pitted the U.S. against NATO ally Turkey as well as Russia and Iran.
The Kurdish majority of the Pentagon-created Syrian Democratic Forces are leaving the U.S. battle against ISIS to fight a Turkish invasion.