A new contest is raging in northern Syria. This time, however, it's not a battle but a race.

On August 24, Turkish tanks and soldiers, backed by U.S. coalition air strikes, crossed the Syrian border to attack positions held by the militant group Islamic State (IS) near Jarablus.

This town lies near the frontier with Turkey and is approximately 95 kilometers northeast of the city of Aleppo.

On the same day, the BBC reported the following:

Military sources told Turkish media 70 targets in the Jarablus area had been destroyed by artillery and rocket strikes, and 12 by air strikes.

Turkish-backed Syrian rebels are accompanying the Turkish advance.

President Recep Tayyip Erdogan said the operation was aimed against both IS and Kurdish fighters.

Despite the fact that Turkey is fighting IS in this area, fighting terrorists may be the mechanism that Ankara is using to engage in northern Syria rather than the primary motivation. Such a scenario envisages Turkey trying to reverse a series of foreign policy defeats it has suffered in recent months, a cycle that has been accelerating in recent weeks.

Aleppo Province is quickly becoming the conflict's most complicated arena. As LiveUAMap illustrates, the region is divided by (at least) six distinct groups of fighters:

Islamic State

Kurdish SDF (northeast)

Kurdish YPG (northwest)

Anti-Assad rebel coalition (in and around Aleppo city)

Free Syrian Army in the Azaz pocket (Turkish border, north of Aleppo)

The coalition supporting Syrian president Bashar al-Assad

The city of Aleppo, once Syria's financial capital, is largely controlled by antigovernment rebel forces and is besieged by a coalition comprising the Syrian military, fighters from Hezbollah, Iranian Islamic Revolutionary Guards Corps (IRGC) commandos, Iraqi Shi'ite militias, and Russian contract soldiers, with the former two groups representing the bulk of the party.

Lately, however, the tables have turned. In the past two weeks, rebel forces, with the help of Al-Qaeda-linked groups, have broken the siege of the city and are now locked in a desperate and bloody battle for the Syrian government's last real stronghold in the north. If the forces loyal to Syrian President Bashar al-Assad lose this fight, the anti-Assad rebels would have a nearly unified front and would be able to push deeper into the regime's heartland.

But the power dynamic in this area is made more complicated by the other competing factions in the region. The westernmost reaches of territory held by IS protrudes north of Aleppo city. To the northeast of the city, the Syrian Defense Forces (SDF) are now rapidly capturing territory from IS. The SDF is made up mostly of Kurdish YPG fighters, although it also contains Arabs and other non-Kurds, and they have been armed, trained, supplied, and otherwise supported by the United States in an effort to create a ground force in Syria that is capable of taking and holding territory from IS. They have taken control of Manbij, about 70 kilometers east-northeast of Aleppo city, and are pushing farther west and south in the process. Crucially, they are also advancing north of Manbij toward Jarablus, the target of Turkey's invasion.

Making things even more complicated, there is another group of anti-Assad rebels that is also predominantly occupied with the fight against IS. Due north of Aleppo city, members of the Free Syrian Army (FSA) control a crescent-shaped sliver of territory sometimes called the Azaz pocket, with their backs to the Turkish border, IS controlling the majority of their perimeter, and a separate group of YPG Kurdish fighters to the west. These FSA fighters are said to have received training, equipment, and support from Turkey and the CIA, but they have been fighting a desperate battle for survival for months.

In the spring, Russian air strikes and ground troops reportedly tipped the balance of power in this region and split the rebel lines in two, cutting off the anti-Assad rebels in Aleppo from the Turkish border, and from the rebels in Azaz. IS, smelling blood in the water, struck north and west, capturing huge amounts of territory from the FSA and other rebel groups. The YPG also saw opportunity, and worked to expand its control in the region.

Since then, the SDF -- which the United States says is made up of more than just YPG fighters but which some analysts say is primarily interested in advancing Kurdish interests in the region -- has benefited from strong support from the United States and has flanked IS. Rebels in the Azaz pocket have capitalized on IS's weakness and have pushed west, but at a snail's pace compared to the advances made by the SDF.

Regional Balance

To simplify: What is taking place in northern Aleppo Province at the moment is effectively a race to see who can capture the most territory from IS the fastest. Just like the end of World War II, when the United States and Britain were advancing into German territory from the west and the Soviet Union was gobbling up the Nazi empire from the east, so too are the Kurds and the various non-Kurdish rebel groups fighting to stake their own claims as IS collapses under the combined weight of its enemies. Just like 1945, the outcome of this race could have major implications for the regional balance of power and could set the stage for the next war in the region, whether hot or cold.

So far, the major losers in this race are arguably the moderate Free Syrian Army (FSA) and Turkey, while Kurdish groups have gained the most. Between 2012 and 2014, the FSA led the fighting against the Assad regime in northern Syria and captured the vast majority of this territory. Between 2014 and 2016, IS seized control of vast swaths of northern Syria. In the last year, foreign support for the Assad military, particularly Russian air power, has helped gobble up even more territory from the anti-Assad rebels. Now, with robust U.S. support, the SDF is capturing that territory and controlling it itself.

In mid-August, Syrian activist Omar Sabbour shared a map made by Syrian journalist Hadi Abdullah that clearly illustrates how much territory has shifted. In 2013, most of northern Syria was covered by the dark-green color of the anti-Assad rebels. IS had yet to be formed, Assad had been pushed out, and the light-green color denoting Kurdish territory was relatively small. In 2014, almost the entire map was gray, having been taken over by IS. But since 2016, the light-green of the Kurds has displaced much of the gray, while Assad's forces have once again entered this zone of control.

The perception among many Syrian activists in this area is that U.S. support for moderate rebels has been lacking while U.S. support for the SDF has been robust. Sabbour's opinion of these developments is strongly worded. “The US has essentially stolen vast swathes of Syria liberated by the FSA between 2012-13 and given them to the YPG. Between 2012-13 -- when these areas were liberated -- the US was actively blockading military supplies coming in from neighboring countries,” he wrote. Since this post, the SDF has advanced even farther.

There are those, of course, who would dispute that worldview. But Sabbour's opinion is not uncommon. Reports suggest there is a sense among many Sunnis that the U.S. government's strategy in Syria and Iraq has empowered Shi'ite and Kurdish groups at the expense of Sunnis who once controlled Iraq and who have always been the strong majority in Syria.

Turkey, a major supporter of the anti-Assad rebels and a country that is effectively at war with the Kurdish PKK and, to a lesser extent (for now) the YPG, has watched as its own proxies have struggled while a group it considers to be a terrorist organization gains power just across its border. Kurdish groups have been blamed for a series of terrorist attacks inside Turkey this summer, including several last week. Jarablus appears to have been the last straw.

Earlier in the week, Turkey fired warning shots, with artillery, at SDF positions in northern Syria. On August 22, the SDF commander of the newly-formed Jarablus military council, Abdulsettar Al-Cadiri, was assassinated after announcing the beginning of the fight for the city. There is no proof for the claim, but there are suggestions that Turkish military intelligence was responsible.

Turkey's engagement in Syria could complicate the situation further, since it is entirely possible that the Turkish military or the rebels it supports could go to open war in northern Syria. Such a development could derail the fight against IS and efforts to end the Syrian conflict, and even widen the war. Any conflict of that nature could also exacerbate sectarian tensions at a time when stability and peace are already at a premium in the region. In short, it's an oil barrel, surrounded by powder kegs, surrounded by flame.

The U.S. government is responding. At the time of writing, the breaking news was that visiting U.S. Vice President Joe Biden had told Kurdish forces that they "must move back across the Euphrates River." He said "they cannot -- will not -- under any circumstance get American support if they do not keep that commitment," according to the AP news agency.

Now there are new questions: Will Turkey continue to expand its operations in Syria? Does this mark a new, much more robust phase of NATO intervention in the conflict? Will Turkey then turn on Assad? Will the SDF and other Kurdish groups respond, or might they lose U.S. support? And how will Russia and Assad respond to their loss of control in northern Syria, which may very likely be permanent?

The race for northern Syria has just heated up. Who will win?