In the weeks leading up to the Turkish invasion of northern Syria, the U.S. military detected a variety of warning signs of a pending massive military operation that showed the Turks were planning to invade no matter what the Trump administration told them, U.S. defense officials say.

Those signs included “things that my military colleagues will point out that doesn’t look like exercising, that doesn’t look like typical garrison behavior; it’s preparing for potential operation,” a senior defense official said during a background briefing Tuesday.

It would have included the movement of thousands of Turkish forces and Turkish-backed Syrian fighters as well as a number of logistical preparations, according to retired Army Vice Chief of Staff Gen. Jack Keane in an interview with Breitbart News Wednesday.

“Conducting military operations that are going to last for weeks over a pretty sizable piece of territory that we’re talking about here in Northern Syria requires a significant amount of logistics preparations,” said Keane.

“So, it’s not only troops; you’ve got to have all of the logistics to support that — and that means food, water, ammunition, fuel — all of that’s got to be moved. And so it’s serious when you see that kind of preparation being made,” he added.

All those things would have shown the degree of seriousness of Turkey’s intent to invade, Keane said.

“They knew they were very serious about it, and it was probably a matter of time. We probably didn’t know exactly what day, but we knew it was inevitable,” he said.

U.S. officials said when Turkish President Recep Tayyip Erdogan spoke to U.S. President Donald Trump on Sunday, October 6, it was to notify him of the imminent invasion — not to ask for permission.

The U.S. decided to pull approximately 24 U.S. Army Special Forces from the area where Turkey was planning to invade — out of concern for their safety.

Keane said there had been ongoing negotiations with the Turks to establish a safe zone in northern Syria — where the Turks were concerned about the presence of Syrian Kurdish forces, who they consider terrorists.

“But Erdogan was frustrated because he didn’t believe these negotiations, which were going on for months … [were] moving fast enough,” he said. “And so I’m convinced he probably had all the preparations to conduct the operation before he called the president, and it was more or less informing the president that he fully intended to conduct this military operation.”

The White House announced the October 6 phone call and the president’s decision to pull back American forces late Sunday evening:

Today, President Donald J. Trump spoke with President Recep Tayyip Erdogan of Turkey by telephone. Turkey will soon be moving forward with its long-planned operation into Northern Syria. The United States Armed Forces will not support or be involved in the operation, and United States forces, having defeated the ISIS territorial “Caliphate,” will no longer be in the immediate area.

Since that call, Democrats and Republicans have blamed Trump for “greenlighting” Turkey’s invasion into Syria by moving U.S. forces back. They argue that if Trump would not have moved the approximately 24 U.S. forces, that Turkey would not have invaded — despite the weeks-long preparations for the campaign.

Trump administration officials argue there was no greenlight and that it was long in coming. Defense Secretary Mark Esper said at a briefing on October 11:

Nobody green-lighted this operation by Turkey — just the opposite. We pushed back very hard at all levels for the Turks not to commence this operation. But Lord knows they have opposed this relationship between the United States and the [Kurdish forces] since its infancy in 2014. The Turks have opposed it all along the way, and so we should not be surprised that they’ve finally acted this way.”

Esper had also urged his Turkish counterpart not to go through with it during a phone call on October 3 — just four days before the operation began.

Chairman of the Joint Chiefs of Staff Army Gen. Mark Milley also spoke to his counterpart that same day. A readout said the two discussed the “importance of U.S.-Turkish cooperation in the region.”

“Despite our protestations, despite the fact that we urged the Turks not to do this, they decided to do it and we told them that we would not support them militarily in this action,” Esper told CBS News on Sunday.

Some, like Keane, believe that Trump should have threatened using U.S. military force to prevent Turkey from moving in.

“I would have said to him … ‘I think that’s a huge mistake on your part … the United States and the coalition controls the airspace in Northeastern Syria, and we are not going to permit you to establish that safe zone by force. In other words, if you come across the border, we will retaliate,’” Keane said.

“And I believe the consequences of that would have been Erdogan is not going to have his fighters fight the United States fighters in the air, or have his militia force deal with the United States-led coalition on the ground, either … because it would have put at risk his ability to establish the safe zone that he wanted,” he added.

Keane said the U.S. would have had to have the conviction that it would retaliate in order to deter Erdogan. “We did not have that conviction, so therefore we did not have any deterrence. Quite the opposite, we moved our forces out of the way.”

Some experts disagree that Trump could have stopped Erdogan.

“I think Turkey would have gone in anyway,” said the Heritage Foundation’s Jim Carafano. “And I think they would have gone in with the confidence that those American forces would have gotten out of the way. That even if the U.S. said, ‘Well we’re not moving our troops,’ that the Turks already made the calculation that the Americans are not going to set up an Alamo.”

“They’re not foolish, they look at our interests, and go, ‘Why would Americans fight over a buffer zone in Syria? I mean, that’s ridiculous. If the Americans said, ‘Well we’re not moving,’ I think they would have seen it as a bluff and gone in anyway,'” he added.

Carafano said the president could have done a better job explaining his decision to the American people and what the strategy going forward was — to stem the waves of criticism leveled at Trump in the days after the phone call for “greenlighting” the operation, however.

“This really calls for a serious speech, for the president to come out and do what he did when he gave the first Afghanistan speech, or when he was pulling out of the Iran deal, and say ‘Look, this is how we got here, this is what’s going on, this is what we’re going to do to protect American interests in the future,'” he said.

But some believe it came down to Trump’s own core opposition to having U.S. troops running around in the Middle East engaged in costly wars.

“It’s more about a 20-year thought that the president has always had about the Middle East,” Keane said. “He’s had this view for some time … his advisers have not dissuaded him from that.”

Carafano said there is only so much the U.S. can do in the Middle East.

“The notion that somehow the U.S. is the architect of this crisis is wrong and that the U.S. can somehow fix Syria is wrong and that the U.S. has anything other than very limited options on how to do this [is wrong],” he said.

“We only really care about two things: One is protecting our forces, the other is we need to continue to counter terrorism fight. The only way we’re going to prevent things like mass refugees [is] by holding the parties accountable for what they do. We’re not going to physically be able to go on the ground to do that,” he said.

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