The Syrian war, now in its 31st month, has transformed into a full-blown proxy war.
The conflict not only involves Syria's neighbors and regional powers, but also Western countries and numerous fighters from more than 25 countries.
We've put together a chart to make sense of the major players backing each side and the infighting that has plagued the opposition to Syrian President Bashar al-Assad.
It's an oversimplication, especially on the rebel side, but provides a basic idea of who's with who:
The side of the Syrian regime is pretty straightforward. Russia has supported them in various forms even before protests began in March 2011.
Iraq has facilitated Iranian supply flights through its territory and placed elite Shia militias under the command of the Qods force (i.e., international wing) of the Iranian Revolutionary Guards (IRGC).
Iran, seeking to protect the Shia crescent that extends from Tehran to Beirut, has been sending troops from its Revolutionary Guards and from its Lebanese proxy Hezbollah while also training Shia militias from Syria, Iraq, and elsewhere. Iranian commanders are increasingly calling the shots on the ground.
Part of Assad's strategy seemingly involved pulling out of northern towns to allow Kurdish fighters to take over, thereby weakening his Sunni enemies.
But some Kurds have chosen to fight the Syrian Arab Army alongside the Free Syrian Army (FSA), and the Kurdish National Council (KNC) formally joined the Western-backed Syrian National Coalition (SNC) in August.
Kurdish fighters affiliated with the Kurdish Democratic Union Party (PYD), meanwhile, have spent much of their time recently fighting al-Qaeda fighters and other Islamic rebels in the north of the country.
After the al-Qaeda-affiliated Islamic State of Iraq and al-Sham (ISIS) overran FSA rebels in the town of Azaz near the Turkish border, Kurdish fighters fought ISIS with the ousted rebels. (Jabhat al-Nusra is considered a separate al-Qaeda affiliate within Syria.)
Interestingly, though it is not listed on the graphic, many in the opposition believe that the Syrian regime have helped bolstered al-Qaeda's presence in Syria to counter the less radical rebels.
Most of the largest Islamist factions recently denounced the SNC and formed Jaish al-Islam ("the Army of Islam") with the blessing of Saudi Arabia. The SNC-affiliated Free Syrian Army was dealt a significant blow by the formation of the Army of Islam but still works with the Army of Islam.
Gulf states, led by Qatar and the Saudis, have been supporting Islamic factions since at least early last year. Private donors in Kuwait also contribute.
There are some rebel groups, most notably Ahrar al-Sham, which fall outside of the bubbles above but also benefit from Gulf donors (primarily via Qatar and Kuwait) and work with other rebel factions.
The SNC remains the only viable political opposition, but almost no one on the ground supports the coalition. Furthermore, the SNC recently rejected peace talks while the Assad's regime doesn't recognize its legitimacy anyway, so a political solution is not an option at this point.
The Israel Defense Force has bombed targets in Syria on several occasions in relation to its own interests. In July 2011 President Shimon Peres said that "Assad must go," but the office of Prime Minister Benjamin Netanyahu recently said that the country's position involves "not intervening in internal Syrian affairs."
Here's the arena where all of these countries and groups are vying for control: