Oren Dorell

USA TODAY

Armies and militias from more than a dozen countries have joined the Syria conflict, making for a mind-boggling and dangerous stew of shifting and competing alliances.

Even as a proposed cease-fire is scheduled to begin as early as this week, more nations are escalating their roles in the nearly 5-year-old civil war: Saudi Arabia, Qatar and Turkey said they may send ground troops to fight.

Here's how different countries are currently aligned:

Pro-Syrian government

Forces loyal to Syrian President Bashar Assad are backed by two nations, Russia and Iran, and many Shiite militias from across the region who are organized by Iran. The combatants include:

Syrian government troops

Iran

Afghan Shiite militia

Hezbollah, the Lebanese Shiite militia

Iraqi Shiite militia

Russia. Russian airstrikes target the Islamic State and what Russia says are other “terrorist” groups. But the U.S. military says most Russian airstrikes are aimed at opposition groups threatening Assad's forces.

Anti-Syrian government

Many rebel forces fighting to overthrow the Syrian government are backed by arms, funds and airstrikes by a U.S.-led coalition. The CIA vetted Syrian rebel groups and helped train them in Jordan to use advanced anti-tank weapons against Assad's forces. Saudi Arabia and Qatar supplied the weaponry and funds. These rebels are being supported by:

Jordan

Saudi Arabia

Turkey

Qatar

United Arab Emirates

United States

Israel, on Syria's southern border, provides some assistance to rebel forces fighting the Syrian government and has also launched airstrikes against Syrian and Hezbollah targets to prevent the transfer of "game changing" technology and weapons to Hezbollah, a U.S.-designated terrorist group.

As Syria cease-fire looms, fighting escalates

Anti-Islamic State

The U.S.-led coalition conducting airstrikes against Islamic State forces in Syria and Iraq includes:

Australia

Bahrain

Canada

France

Jordan

Saudi Arabia

Turkey

United Arab Emirates

United Kingdom.

Russia is not part of the U.S.-led coalition, though it has also hit Islamic State positions.

U.S. airstrikes against Islamic State grow more lethal in Iraq

Other fighters

Kurdish militia from Turkey, Iraq and Syria are fighting the Islamic State, also known as ISIL or ISIS. But the Kurds are sometimes aligned with the Syrian government and seen as a threat by Turkey, which has fought for years against a Kurdish separatist movement threatening its territorial sovereignty. Syrian Kurds are backed by Russia, the United States and Iraqi Kurdish groups.

The Islamic State, a vicious al-Qaeda spinoff, and Jabhat al Nusrah, al-Qaeda’s branch in Syria that works with many Sunni Arab opposition groups in Syria, have attracted foreign fighters from across the Arab world and Europe. Both have expanded during the chaos in Syria.