With Turkey’s invasion of Syria, concerns are beginning to mount over the United States' nuclear weapons in Turkey. But why does the US have nuclear weapons in a foreign country?
Senior US officials are arguing about whether they should pull the United States' nuclear arsenal from Turkey as the situation deteriorates along the Turkish-Syrian border in the wake of Turkey's attack on the Kurds.
This week Turkey announced it had annexed a "safe zone" inside Syria after launching an all-out assault on Kurdish forces earlier in the month. But with the situation now switching from open combat to a police action aimed at removing Turkey's longtime enemies, the Kurds, concerns are mounting about what that means for the US nuclear stockpile in Turkey.
According to a New York Times report, senior US State and Energy Department officials met last week and are now reviewing plans to potentially evacuate about 50 tactical nuclear weapons that America has stored at the Incirlik Air Base in Turkey since the height of the Cold War.
While the location was once a potential axis of advance if the Cold War against the Soviet Union suddenly got hot, it is now just 400km from the unstable Syrian border where Turkish and Kurdish troops continue to clash, sparking concerns the weapons of mass destruction could fall into the wrong hands.
One senior official told the New York Times those nuclear weapons are now being effectively held hostage by the Turks.
"To fly them out of Incirlik would be to mark the de facto end of the Turkish-American alliance. To keep them there, though, is to perpetuate a nuclear vulnerability that should have been eliminated years ago," they told the newspaper.
"I think this is a first — a country with US nuclear weapons stationed in it literally firing artillery at US forces," Jeffrey Lewis of the James Martin Center for Nonproliferation Studies wrote last week.
Mr Lewis was referencing several near misses experienced by withdrawing US troops, including a recent Turkish air strike which narrowly missed US troops.
So why does the US have nukes in a foreign country?
Turkey has long been a literal launchpad for the US's nuclear capability, most notably the PGM-19 Jupiter nuclear tipped missiles President John F Kennedy had to secretly withdraw from the country in the wake of the 1962 Cuban Missile Crisis.
As part of the secret US-Soviet agreement, President Kennedy pulled the aging missiles out of Turkey in exchange for the Soviets withdrawing their own from Cuba, defusing one of the tensest situations of the entire Cold War.
Incirlik, a joint US-Turkish base, was established in the 1950s and effectively gave the US the ability to deploy nuclear weapons against the Red Army if the Soviets did ever attempt a conventional attack through Europe. Most recently it played a key part in the US air attacks on IS in Syria.
The US has never openly admitted to storing nuclear weapons on the base, but it is effectively an open secret.
While nuclear weapons served a battlefield purpose, their real worth was – and still is - political, according to University of Queensland's Dr Sarah Percy.
"It's partially an alliance reassurance, to show Turkey that is has an ally in the USA… and it’s partially a holdover from that Cold War school of thinking," the professor, who specialises in the Cold War for the university’s school of political science and international studies, told SBS News.
"Providing a reassurance that if something happens to that country, the US will honour its alliance is very important.
"The strategic logic behind nuclear weapons is very interesting – the Germans and the French and other NATO allies wanted that reassurance that if the Soviets dropped nuclear weapons on Paris or their capital, then the US would honour its alliance, even though it’s not been directly attacked."
At the peak of the Cold War in the mid-1970s, the US had an estimated 7,000 tactical nuclear weapons spread across Europe – including 500 in Turkey – to counter a potential Soviet attack and reassure its allies it was committed to their defence.
Dr Percy said the nuclear weapons in Turkey were highly unlikely to ever get deployed or used – but the weapons served a greater purpose off the battlefield: as political bargaining tools.
"They’re effectively redundant, but nuclear weapons are great bargaining chips – politically, nuclear weapons are very, very significant," she said.
She said the eyes of the world were constantly on the US's nuclear stockpile and any increase in numbers triggered similar steps in places like Russia. By keeping the Turkey-based weapons, only to move or scrap them at an advantageous time, US President Donald Trump could call for concessions from other countries when he most needs it.
President Trump effectively owned up to the open secret of nuclear weapons in Turkey during a recent press conference, when asked if he was worried about the security of "as many as 50 nuclear weapons at Incirlik Air Base" due to the ongoing Turkish incursion into Syria
"We're confident, and we have a great - a great air base there, a very powerful air base. That air base alone can take anyplace. It's a large, powerful air base," he responded.
Dr Percy said the Cold War mentality of stationing nuclear weapons in allied countries to keep those countries from building their own WMDs could also still be influencing the decision.
"If you keep them (nuclear weapons) there, does that persuade (Turkish President Recep Tayyip) Erdogan from starting his own nuclear program?"
"Maybe, although Erdogan certainly seems to think he has the upper hand in dealing with Donald Trump."
But those concerns have taken on a new urgency in the wake of Turkey's actions in Syria
"The next question to Trump and Department of Defence should be why is the United States continuing to store nuclear weapons in Turkey given that Turkey is an increasingly unreliable ally," the director for disarmament and threat policy at the US Arms Control Association, Kingston A. Reif, said in a recent interview with CNN.
He said the "proximity of the weapons to a war zone" added a whole new dimension to nuclear politics.
What kind of nukes does the US have in Turkey?
While the Pentagon never publicly reveals information about its nuclear arsenal, it has been reported the 50 nuclear weapons in Turkey are B61 gravity bombs – tactical nukes that can be dropped from US Air Force F-16 Strike Fighters or British Tornado fighters.
Another 130 B61 bombs are stationed in NATO bases across Europe, including in Belgium, Germany, Italy and the Netherlands.
At the height of the Cold War, the Soviet Union’s "Red Army" was the largest conventional military in the world and boasted between 2.8 and 5.3 million men. Following WWII, as the two super powers began their face off, the Soviets could have effectively rolled over any of its pro-West allies and the US came to increasingly rely on the threat of nuclear weapons to keep the peace.
While a first-strike attack – either from a long range bomber or a submarine popping up from beneath an Arctic ice shelf was always the preferred method - the US used its European stockpile, including the Turkish arsenal, as a way to level the conventional playing field if it ever came to tanks and soldiers fighting it out.
The debate about what to do with the US’s nuclear weapons comes as Turkish President Recep Tayyip Erdogan announces he wants his own nuclear weapons.
“Some countries have missiles with nuclear warheads,” he told a meeting of his governing party in September, before going on to say the US and western allies insist "we can’t have them".
"This, I cannot accept."
On Monday, the US Air Force told the Air Force Times the Incirlik Air Base had not changed its daily operations, despite the border clashes.
“The mission of the 39th [Air Base Wing at Incirlik] is to provide persistent surety and continuous air operations for the US, our allies and our partners and helps protect US and NATO interests in the Southern Region by providing a responsive and operational air base ready to project integrated, forward-based airpower,” a US Air Force spokesperson told the Air Force Times.