Many world leaders have grown increasingly determined to destroy the self-described Islamic State, especially since the Nov. 13 terror attacks on Paris killed 130 people -- but Turkey shooting down a Russian Su-24 bomber plane that had allegedly moved from Syria into Turkish airspace on Tuesday has complicated this goal.
Here's what you need to know.
Who's To Blame?
It's still not clear where the Su-24 was when it was shot down.
The Turkish government says the plane violated its country's airspace. Authorities "repeatedly warned an unidentified aircraft that they were 15 km or less away from the border," a Turkish government official told The WorldPost.
But a Russian pilot who survived the attack said Wednesday that the airmen never received warnings from Turkey, and Russia has maintained that the plane was shot down in a "planned provocation" over Syrian airspace.
"Our pilots and jet posed no threat to the Turkish Republic. This is obvious. They were conducting an operation against [the Islamic State]," Russian President Vladimir Putin said Tuesday.
Putin also condemned Turkey's decision to contact NATO members in the wake of the attack instead of reaching out to Russia directly, calling the incident "a stab in Russia's back."
Russian Foreign Minister Sergey Lavrov claimed Turkey was provoked by threats to its illegal oil interests. Russian planes, he said, had struck Islamic State oil infrastructure, and Turkey was angered because it "benefited from the oil trade."
World Leaders Call For Restraint
Many fear that escalated tensions will derail the Syrian peace process.
"What we must hope for is that this occurrence will not deal a setback to the encouraging first talks, which offer a small hope of de-escalating the Syrian conflict," German Foreign Minister Walter Steinmeier said Tuesday. He also asked Turkey and Russia to take joint responsibility.
"We are calling for calm and de-escalation. This is a serious situation," NATO Secretary General Jens Stoltenberg said during a press conference in Brussels, Belgium. He also called for "further contacts" between Russia and Turkey in order to increase transparency and avoid these types of scenarios in the future.
"The common enemy should be ISIL," he asserted, using an alternate name for the Islamic State.
President Barack Obama echoed the call to focus on dismantling the Islamic State in Syria.
"This points to an ongoing problem with the Russian operations in the sense that they are operating very close to a Turkish border and they are going after moderate opposition that are supported by not only Turkey but a wide range of countries," he said Tuesday during a joint press conference with French President François Hollande.
Russia And Turkey Are At Odds Over Syria
Turkey has made calls to oust Syrian President Bashar Assad from power, but it also has a history of bombing Kurdish opposition fighters in Syria who are believed to be linked with the Kurdistan Workers' Party (PKK) and the Kurdish People's Protection Units (YPG). Both parties lobby for Kurdish autonomy, and Turkey fears that an autonomous Kurdistan will encourage separatism among Turkish Kurds.
There was a bombing last month in the Turkish capital of Ankara that Turkey's president, Recep Erdogan, blamed on both the Islamic State and Syrian Kurds, even though Syrian Kurdish groups are fighting the Islamic State in Syria.
Russia, on the other hand, supports Assad's rule. Although Putin advocated for an international coalition against the Islamic State during his U.N. General Assembly speech in September, he has carried out airstrikes in Syria that instead target opposition groups, further bolstering the Assad regime.
Ties between Russia and Syria are decades-old. When former Syrian President Hafez Assad took power in the 1970s, he negotiated an arms trade deal between the two countries. Russia is currently Syria's largest weapons supplier.
Geopolitics also play a role. If Putin were to demand Assad's departure, he would be "retreating under American pressure, which is the one thing he cannot do," Georgy Mirsky of Moscow's Higher School of Economics told the Economist.
As A Result, Building An International Coalition To Fight The Islamic State Becomes More Difficult
Putin ordered air-defense missiles to be deployed at a base in Syria's Latakia province Wednesday, which would allow Russia to shoot down Turkish jets with more precision. Russia's Defense Ministry also decided to sever its military contracts with Turkey.
However, Russia says it has no interest in entertaining the idea of war.
"We are not planning to wage a war against Turkey, our attitude towards Turkish people has not changed," Russian Foreign Minister Sergey Lavrov said Tuesday, adding that Russia is merely defending itself.
Steven Cook, senior fellow for Middle East and Africa Studies at the Council on Foreign Relations, said "this isn't at all like the Cold War."
"We will likely hear a lot of threats from Putin in the coming days," he added, "but as Lavrov said, there will not be war with Turkey. Moscow will possibly try to exact revenge by supporting the PKK and/or the YPG."
Turkey wishes to maintain its ties with Russia but is not apologetic about the incident, Turkish Prime Minister Ahmet Davutoglu said Wednesday.
"Russia is our neighbor, friend and very important partner," he said. "We have no intention to sever ties or fan tensions in connection with this incident. But we have the right to protect our borders and will be using it further on."
Meanwhile, the Western states leading the fight against the Islamic State have hoped that recent events -- such as the Russian airliner shot down over Egypt by Islamic State militants and the attacks on Paris -- will convince Russia to align with them.
Hollande said he will travel to Moscow on Thursday to press Putin to fight the Islamic State.
"He will try to de-escalate tension and seek military coordination with the Russians," Cook said.
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