Turkey has been a long time ally of the USA and a member of NATO since 1952. It is a nation with a population of 80 million and maintains the largest armed force in NATO. in short, it is a pivot of NATO. Turkey since the time of Kemal Ataturk has always allied with the west and at one time was a front line state against the Soviet Union. The Turks allowed nuclear weapons to be stationed on their soil for a possible retaliation against the Soviet Union.
As things stand the Incirlik air base in Turkey is the major strike base of the US Air Force and houses the F-15 and F-16 for operations against the ISIS and strikes against Assad in Syria. It houses about 50 nuclear warheads called the Jupiter B-1. The base is in focus now as after the attempted military coup in Turkey against Erdogan the Turks enforced a "no fly" zone and no aircraft of the USAF could fly for any mission. Only those aircraft which were on a mission were allowed to land back.
TheIncirlik base houses the headquarters of the US air force central command and has hangers and silos for the F-16/15 plus the nuclear bombs. The base was exposed as the President of Turkey Erdogan assumed ( he may have got reliable information) that the coup attempt by the military against him was engineered by the CIA. Much of this information to Erdogan was supplied by the Russians who had eavesdropped on the chatter on the radio ( in code) between the coup plotters and some officials of the CIA.
In addition, a cleric named Gulen, who is in self-imposed exile in the USA was thought by Erdogan to be part of the coup. Erdogan has asked for the handing over the cleric which has been refused by the US. This has led to bitterness and has seen the Turkish president proceed to Russia to mend fences with Putin. It may be recalled that the Turks had shot down a Russian fighter a few weeks back and relations had soured. The visit by Erdogan changed all that as he apologized for the shooting and made overtures to Russia.
Erdogan was extremely unhappy with the USA and he took it out on the US base. He not only imposed a no-fly zone but cut off external power to the base. This is a critical requirement and the base had to be run on internal power. The 2000 odd servicemen of the US armed forces were advised by the US command not to venture out of the base perimeter. In addition, special guards were posted for the nuclear assets.
The vulnerability of the base was exposed and it was the cause for alarm in the Pentagon. The actions of Erdogan became unpredictable as he set about arresting thousands of soldiers and other citizens who he thought had links with Gulen, CIA or the coup plotters. The commander of the Turkish airforce on the base was also arrested. These actions showed to the USA that nothing could be taken for granted. The base which is just 70 miles from the Syria border is extremely vulnerable to Jihadi attacks and there is a real danger of this WMD falling into the hands of the Jihadi elements or worse if Erdogan decided to appropriate the nuclear weapons for himself. The stationing of nuclear weapons in an unstable country by the USA is fraught with danger and now the Pentagon has realized what a blunder they have committed.
The Incirlik base is in the eye of the storm. A distrust has developed between the Turkish elements loyal to Erdogan and the coup plotters. The US secretary of State Kerry has called for restraint to Erdogan on his arresting thousands of so-called coup supporters. The arrested are close to 100,000. Erdogan is also planning to re-introduce the death penalty and that is cause for alarm to the EU. Erdogan would like to hang all the coup plotters so he can cement his rule. But history has shown that such dictators invariably fall as after 11 years of the rule even General Zia ul Haq of Pakistan was assassinated when his C-130 Hercules was crashed by incapacitated pilots. So Erdogan needs to worry in the aftermath of the coup.
The real cause of worry will, however, remain for the US. With Erdogan flirting with Russia and an unstable Turkey the nuclear weapons are at great risk. The USA was planning to remove them to Romania, but the plan has not been affected as yet. The weapons remain on the base and are a cause of great worry. One wonders when will the USA learn that there are no permanent allies only interests and Erdogan is like a bull in a China shop. He cannot be stopped except by another coup.
Image source https://en.wikipedia.org/wiki/Recep_Tayyip_Erdo%C4%9Fan