"I don't understand how a president that claims he's the toughest President ever would do such a weak move like this," Representative Adam Kinzinger said.
"This is heart-rending for anybody who has shed blood, who has deployed forward," former NATO Supreme Allied Commander James Stavridis said.
Some 2,500 ISIS foreign fighters remain in Kurdish prisons in northeastern Syria, but the Turkish operation may threaten the security of such facilities.
Allowing Turkey to act against the Kurdish-led SDF in northeastern Syria "will severely damage American credibility," retired General Joseph Votel said.
"The fight against Daesh [ISIS] is not over and continues alongside the [Kurdish-led] Syrian Democratic Forces," Prime Minister Edouard Philippe said.
"We are voluntarily abdicating our role and it's the Russians, Iranians and others who are benefitting," Richard Haass warned.
The former U.S. Ambassador to the United Nations said the decision was "appalling" because Kurds had been "promised our partnership."
The president told reporters Monday that an unnamed "top general" lamented the state of U.S. military supplies when he took office.
An intelligence official told Newsweek about Trump's phone call with the Turkish leader, saying the U.S. president was "out-negotiated."
"By abandoning the Kurds we have sent the most dangerous signal possible – America is an unreliable ally," the Republican senator from South Carolina argued.
"Donald Trump is not a Commander-in-Chief. He makes impulsive decisions with no knowledge or deliberation," McGurk said on Twitter.
The White House has said Turkey will now be responsible for ISIS prisoners held by the Kurds, but an invasion of northern Syria could unleash chaos that ISIS fighters would try to exploit.
A former U.S. special envoy to the coalition against ISIS was among many critics of the move, saying that decision to allow Turkey's incursion "guaranteed future bloodshed".
Abdul-Majeed Marouf Ahmed Alani, 60, who allegedly disabled a navigation system on a flight from Miami International Airport, was denied bond on Wednesday.
Judge Anthony Trenga ruled Wednesday that the federal government's Terrorist Screening Database violates due process.
One of the women has also declared that she and her bomb-making collaborator are "citizens of the Islamic State," according to the FBI.
Canadian politicians might not be able to save "Jihadi Jack" from a Kurdish prison, where he has been held for two and a half years.
The 34-second clip, promoted by al-Qaeda to mock its competitor, shows that even radical terrorists can get camera shy.
The Christchurch shooter mentioned only one U.S. state in his manifesto: Texas. The El Paso shooter answered this online call to arms.
Americans' fears of North Korea's nuclear program and the Islamic State have both fallen significantly in the past two years of Donald Trump's presidency.
Salah Abdeslam is serving a 20-year sentence for his role in the terrorist atrocities committed in November 2015.
Alexanda Kotey, radicalized in West London, was one of four members of the notorious torture cell, infamous for their brutality and British accents.
El Shafee Elsheikh is one of three remaining members of the group that killed U.S. journalists James Foley and Steven Sotloff.
Rodrigo Duterte, president of The Philippines, made the comments during a visit to soldiers hurt in a recent firefight with ISIS-linked Abu Sayyaf.
Are YouTube and Snapchat down, not working? Entire regions of U.S. affected by social media outage.
Alexander Bortnikov, head of the Federal Security Service, warned that 5,000 fighters from ISIS had been deployed in northern Afghanistan.
ISIS eventually occupied the site meant to host Syria's nuclear reactor. If Israel hadn't destroyed it seven years earlier, ISIS might have been able to inflict destruction on an almost unimaginable scale.
Robert Francis Pratersch faces 15 years in jail after threatening to kill the 2020 Democratic presidential candidate.
"The battle of Baghouz is finished, but it demonstrated the barbarity and savagery of the crusader community towards the Muslim community," ISIS chief Abu Bakr al-Baghdadi appeared to say on tape.