In the immediate aftermath of the failed Turkish "coup" of July 2016, the immediate concern to the US was not the fate of the Erdogan regime, but whether the US would maintain access to Incirlik Air Base, a strategic output for the US airforce, allowing it fast and easy access to most of the Middle East and part of Russia even in the immediate absence of an aircraft carrier. It explains why when Erdogan said he felt snubbed by the US, he cut off the power to the US troops stationed at the airbase, and kept them in the dark for a considerable period of time, perhaps to remind Washington that in Turkey he is the boss.

Fast forward to this week, when on Wednesday, Turkish officials again made a veiled threat to ground U.S. warplanes at Incirlik Air Base over the U.S. denial of air support for the Turkish military inside Syria. The officials questioned the value of having the U.S. fly missions out of Incirlik in southeastern Turkey against ISIS targets in Syria and Iraq while Turkish forces are struggling to take the ISIS-held Syrian town of El Bab.

"This is leading to serious disappointment in Turkish public opinion," Turkish Defense Minister Fikri Isik said, adding that "this is leading to questions over Incirlik," Turkey's Anadolu news agency reported.

He then once again treatened the US, when he said that to avoid repercussions that could affect Incirlik operations, the Defense Minister called on the U.S. to "start to provide the aerial support and other support that the [Turkish military] needs" to take El Bab, which would also drive a wedge between Syrian Kurdish militias supported by the U.S. in actions against the Islamic State of Iraq and Syria.

U.S. Air Force Col. John Dorrian said Wednesday than any actions by Turkey to shut down or limit U.S. air operations out of Incirlik would be disastrous for the U.S. anti-ISIS campaign now focused in Syria on the drive by a mixed Syrian Kurdish and Arab force against Raqqa, the self-proclaimed ISIS capital. What he meant to say is that it would disastrous for the U.S., period, as it would deprive the US of one of its most critical military outputs in the MENA region.

12 F-15s from RAF Lakenheath, UK are deployed to Incirlik AB, Turkey, November, 2015

"It's absolutely invaluable," Dorrian, a spokesman for Combined Joint Task Force-Operation Inherent Resolve, said of Incirlik. "Really, the entire world has been made safer by the operations that have been conducted there." Well, that or precisely the opposite - it all depends on one's point of view.

Turkey briefly closed its airspace to U.S. operations out of Incirlik last July and cut off power to the base during the failed military coup against the government of President Recep Tayyip Erdogan when suspicions ran high among Turkish officials that the U.S. may have supported rebels within the military. As the coup attempt failed, a high-ranking Turkish officer walked across the Incirlik airfield and tried to turn himself into the U.S. military to seek asylum. His request was rejected, and he was arrested by Turkish authorities.

On Wednesday, Turkish Foreign Minister Mevlut Cavusoglu said, "The U.S. is a very important ally for us. We have cooperation in every field, but there is the reality of a confidence crisis in the relationship at the moment" over Incirlik and the El Bab offensive, which Turkey has named Operation Euphrates Shield. "Our people ask, 'Why are they [the U.S. and coalition warplanes] using the ?ncirlik air base' " if they won't back up Turkish forces against ISIS and the Kurdish militias considered terrorists by Turkey? "What purpose are you serving if you do not provide aerial support against [ISIS] in the most sensitive operation for us?"

U.S. officials have confirmed they are withholding airstrikes from the El Bab offensive while maintaining overall support for Turkey's anti-ISIS efforts inside Syria, aimed at sealing off border areas. On Tuesday, Pentagon Press Secretary Peter Cook said that U.S. aircraft flew near El Bab on Monday but did not conduct any strikes. In a briefing from Baghdad to the Pentagon on Wednesday, Dorrian suggested that weather and poor intelligence on the disposition of friendly forces may have been a factors in the decision not to attack.

"The cardinal rule of air support is to do no harm," Dorrian said, adding that the aircrews may not have had "good fidelity" on enemy positions. The result was "a show of force that was conducted at the request of Turkish forces operating on the ground," he said.

Quoted by Military.com, Dorrian said that "there were ongoing discussions at higher levels "to increase the support and operations" by the U.S. military to back Turkish forces, but "I can't get ahead of those discussions. I don't have the details to offer you about what the way forward will be in El Bab. But I do know there has been some good discussion on that, and Turkey is aware of that discussion," he said.

The loss of Incirlik air base would be a tremendous hit to US influence in the region.

The U.S. Army Corps of Engineers began construction in 1951 of what was to become Incirlik Air Base, and U.S. and Turkish air forces signed an agreement in 1954 for joint use of the base. Incirlik long served as a deterrent to the then-Soviet Union and as a staging base for U.S. operations in the Mideast.

Despite recurring reports that US nuclear weapons are store in the base, the U.S. Air Force will neither confirm nor deny. About 5,000 U.S. service members, mostly Air Force, are based at Incirlik; they are currently confined to the base because of unrest in the region. The U.S. last year withdrew military families from Turkey, and the State Department has also sent home non-essential personnel.

The tensions over El Bab and Incirlik have only added to the downward spiral of relations between the U.S. and NATO ally Turkey, marked by Erdogan's new alliance with Russian President Vladimir Putin to bring about a ceasefire and peace talks to end Syria's nearly six-year-old civil war. As reported last week, the U.S. was not invited to a Moscow meeting last month of the foreign ministers of Russia, Turkey and Iran that led to Putin's announcement last week of the ceasefire and possible peace talks later this month in Astana, Kazakhstan, with rebel groups.

Turkey has also been angered by what it sees as U.S. foot-dragging on its extradition request for exiled Muslim cleric Fethullah Gulen, now living in Pennsylvania. Erdogan has blamed Gulen for fomenting the July coup attempt. In addition, Erdogan has bridled at U.S. support for the Syrian Kurdish militia known as the YPG, or People's Protection Units. The YPG has proven to be the most effective fighting force against ISIS in Syria, but Erdogan considers it an arm of the Kurdish PKK, or Kurdistan Workers Party, which has been branded a terrorist group by the U.S. and Turkey.

A senior U.S. military official, speaking on background last month, told Military.com that the Turks "hate that we support" the YPG.

Erdogan and other Turkish officials have charged that the U.S. is supplying weapons to the YPG. The U.S., while acknowledging support for the YPG, has denied giving them recent supplies of weapons.