The United States's relationship with Turkey hit a low point this week after a rift over a Russian missile system that has taken the two nations’ alliance to a new level of animosity.

Washington on Wednesday officially booted Ankara from the F-35 fighter jet program over the NATO ally’s purchase of the Russian S-400 surface-to-air missile defense system.

The move drew the ire of Turkey, whose government said the move went counter to the “spirit of alliance,” and called on Washington to reverse the decision.

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“We call on the United States to come back from this mistake that will cause irreparable damage to our strategic ties,” Turkey’s Foreign Ministry said in a statement.

But the Trump administration’s move was hardly a surprise as it has threatened such retaliation for months if Turkey took delivery of the first shipment of S-400 parts, which it did on July 12.

This also marks yet another fracture in the relationship between the two nations, after years of brewing tensions and deteriorating goodwill marked by disagreements over foreign allies, sanctions and leadership style.

Here are five things to know about the latest rift and previous clashes between the two countries.

Turkey is breaking with NATO

Turkey's President Recep Tayyip Erdoğan defied strong objections from the U.S. and NATO countries in buying the S-400.

Erdoğan insisted it was his country's sovereign right to buy and defend itself with the Russian system.

But the purchase has lasting implications for the relationship between the two countries and the larger NATO alliance, which can no longer count on Turkey to help it defend its skies.

“Turkey has been a longstanding and trusted partner and NATO Ally for over 65 years, but ... This will have detrimental impacts on Turkish interoperability with the Alliance,” the White House said in a statement released Wednesday.

“The F-35 cannot coexist with a Russian intelligence collection platform that will be used to learn about its advanced capabilities.”

Also now in question is whether the F-35 and other stealth aircraft will no longer be able to fly in Turkish airspace, which is sometimes used during operations in Iraq and Syria.

Deputy Undersecretary of Defense for Policy David Trachtenberg, said Wednesday that the alliance between Washington and Ankara will continue, but would not say whether the alliance would be weakened by Turkey’s inability to participate in the integrated air defense of NATO.

The relationship may be further soured by congressionally mandated sanctions, which the S-400 buy has triggered.

The penalties fall under the Countering America’s Adversaries Through Sanctions Act and are imposed when a U.S. partner buys Russian military equipment.

President Trump Donald John TrumpFederal prosecutor speaks out, says Barr 'has brought shame' on Justice Dept. Former Pence aide: White House staffers discussed Trump refusing to leave office Progressive group buys domain name of Trump's No. 1 Supreme Court pick MORE said Thursday that he has not yet made a decision on whether to impose the sanctions.

Issues over Kurds drive Turkey's decision

Turkey for years stridently disagreed with the U.S. policy of providing weapons, training and support to Syrian Kurds known as the Syrian Democratic Forces (SDF), to fight ISIS militants.

The effort, initiated during the Obama administration, bolsters a group that hopes to eventually carve out an independent state in northeastern Syria, which borders Turkey, where it has been fighting ISIS.

But Turkey views the group as terrorists and has threatened to attack the population, even going so far as to launch an invasion of the Kurdish-held territory of Afrin last year.

The threat has kept U.S. troops in Syria, though Trump is itching to pull them out.

Trump in December first sought to withdraw all U.S. forces from Syria immediately, plans that the administration has since walked back.

Officials worry that should troops leave, Turkey will take the opportunity to attack the population.

The U.S. now seeks a promise from Turkey that it won't move in on the SDF and launch a broad campaign of repression should it leave the region, but that assurance has yet to come.

Officials have been icy toward each other over the rift, with Turkey going so far as to refuse to meet national security adviser John Bolton John BoltonJudge appears skeptical of Bolton's defense of publishing book without White House approval Maximum pressure is keeping US troops in Iraq and Syria Woodward book trails Bolton, Mary Trump in first-week sales MORE in January, after he demanded assurances.

U.S.-Turkey tensions were already brewing

The relationship between the two countries were already frayed by the time of the S-400 sale, in part due to the Turkish government’s imprisonment of American pastor Andrew Brunson.

Turkey accused Brunson of being behind the failed 2016 coup, which sought to overthrow Erdoğan, and imprisoned him for two years.

In retaliation, the Trump administration imposed sanctions and tariffs on two top Turkish government officials.

The penalties, though mostly symbolic, damaged the Turkish economy and caused a deeper rift between the two countries, with Erdoğan saying that U.S. officials “are trading a strategic NATO ally for a priest.”

Turkey relented and in October released Brunson but still convicted him for what it claimed was aiding terrorism.

Turkey is backing Venezuela and advocating for drop in Iranian sanctions

Turkey is among a handful of countries, including China and Russia, backing Venezuelan President Nicolás Maduro as his country has descended into humanitarian and economic crises.

The position makes it an outlier among NATO members, including the United States, which is among roughly 50 countries that recognize opposition leader Juan Guaidó as Venezuela’s rightful leader.

With an eye on ousting Maduro, the United States in recent months has imposed sanctions on Venezuelan businesses and those close to the leader, which Turkey has condemned and called anti-democratic.

Causing more stress, Turkey continues to trade with Maduro's government, propping it up as the United States works to diminish it.

Ankara has also repeatedly criticized Washington for its decision to reimpose sanctions on Iranian oil over perceived violations of the 2015 nuclear deal — a move that hurts Turkey as it does not have its own reserves and must import oil and gas.

Controversial cleric fuels anger

Following Turkey's failed 2016 coup, more than 77,000 people have been jailed — the majority military personnel, police, journalists, lawmakers, judges and prosecutors — with widespread arrests routine and closure of hundreds of media outlets.

Erdoğan, in particular, has blamed a U.S.-based cleric, Fethullah Gülen, for being responsible for the coup attempt and said the arrests were on suspected collaborators to the cleric.

The Turkish government for years has pressured the Trump administration to extradite Gülen, who has lived in self-imposed exile in America for almost 20 years. At one point the government dangled Brunson's release as a bargaining chip.

But the U.S. has refused to hand over Gülen, which has angered Erdoğan and pushed the two countries further apart.