Syria's war is a mess.
After four years, the conflict is divided between four different sides on the ground.
Each side has foreign backers, and those foreign backers don't even agree with each other about who they're fighting for, or who they're fighting against.
To understand all this -- the criss-crossing interventions, the moving battle lines --
it helps to go back to the beginning of the war and watch how it unfolded.
The first shots in Syrian's war are fired, in March of 2011, by Syrian dictator Bashar al-Assad against
peaceful Arab Spring demonstrators.
In July the protesters start shooting back, and some Syrian troops even defect frin Assad's army to join them.
They call themselves the Free Syrian Army and the uprising becomes a civil war.
Extremists from Syria and from around the region start traveling to Syria to join the rebels.
Assad actually encourages this by releasing jihadist prisoners to tinge the rebellion with extremism
and make it harder for foreigners to back them.
In January 2012, al-Qaeda forms a new branch in Syria, Jabhat al-Nusra.
Also around then, Syrian Kurdish groups, who've long sought autonomy, take up arms an de facto secede from Assad's rule in the north.
That summer is when Syria becomes a proxy war. Iran, Assad's most important ally, intervenes on his behalf.
By the end of 2012, Iran is sending daily cargo flights and has hundreds of officers
on the ground.
At the same time, the oil-rich Arab states on the Persian Gulf begin sending money and
weapons to the rebels, mainly to counter Iran’s influence, and mainly through Turkey.
Iran steps up its influence, in turn, in mid-2012 when Hezbollah - which is a a Lebanese Shia group backed by Iran -
invades to fight alongside Assad.
The Gulf states respond by sending even more money and weapons
to the rebels -- Saudi Arabia really leading the effort at this point -- this time through Jordan who also opposes Assad.
By 2013, the Middle East is divided between generally Sunni powers on one side supporting the rebels
and Shiahs on the other side supporting Assad.
That April, the Obama administration, horrified by Assad's atrocities
signs a secret order authorizing the CIA to train and equip Syrian rebels.
But the program stalls out at first.
At the same time, the US quietly urges the Arab Gulf states to stop funding extremists, but their requests go ignored.
In August, Assad uses chemical weapons against civilians in the town of Ghouta.
Obama: "Men, women, and children lying in rows – killed by poison gas..."
It is in the national security interests of the United States to respond to the Assad regime's use of chemical weapons
through a targeted military strike.
Russia proposed on Monday that Syria surrender control over its chemical weapons to the International Community
for its eventual dismantling, to avoid a US military strike.
The US ends up backing down but the whole thing establishes Syria as
a great-powers dispute -- with America against Assad and Russia backing him.
Just weeks later, the first American training and arms finally reach Syrian rebels.
The US is now a participant in the Syrian war.
In February 2014, something happens that transforms the war: an al-Qaeda affiliate, based mostly
in Iraq, breaks away from the group over internal disagreements over Syria.
The new group calls itself the Islamic State of Iraq and Syria, and it becomes al-Qaeda's
enemy.
ISIS doesn't fight Assad. Instead, it fights the other rebels and it fights the Kurds, carving out a mini-state
in Syria it calls its Caliphate.
That summer, it marches across Iraq seizing territory, and galvanizing the world against it.
Then in September, almost exactly one year after it had almost bombed Assad in Syria....
Obama: We're moving ahead with our campaign of airstrikes against these terrorists,
and we're prepared to take action against ISIL in Syria as well.
That summer, in July, the Pentagon launches its own program to train Syrian rebels —
but unlike the CIA program -- this one will only train rebels that those fight ISIS, not Assad.
The program fizzles out, showing that America now opposes ISIS more than Assad,
but also that there's really no like-minded force on the ground in Syria.
In August, Turkey begins bombing Kurdish groups in Iraq and in Turkey,
even as the Kurds str fighting ISIS in Syria. Turkey also doesn't bomb ISIS in Syria.
All of this deepens tensions with the US over this question of whether they need to see Assad or ISIS as the primary enemy.
And this creates a lot of confusion with the Kurds about where the US stands.
Now, Assad has been losing ground all this time to to ISIS to the rebels
And in September of 2015, Russia intervenes on his behalf.
Russia says it's there to bomb ISIS, but in fact just bombs the anti-Assad rebels,
including some backed by the US.
So as it stands now, there are lots of different groups and outside countries involved in Syria's war
and even among allies there are big disagreements about
who their enemies are, who to support and how to do it.
And those contradictions are a big reason why -- for this war --
there’s just no end in sight.