Kayla Mueller was one of the four Americans whose murder by the Islamic State (ISIS) President Donald Trump described as “especially heinous” on Sunday morning when he announced the appropriately cowardly demise of the man who ordered them tortured and murdered, Islamic State leader Abu Bakr al-Baghdadi.

National Security Adviser Robert O’Brien said on NBC’s Meet the Press Sunday morning that the mission to take out Baghdadi was named after Mueller.

“We finally brought justice to a man that beheaded the three Americans, two journalists and a humanitarian worker. And Kayla Mueller who was working as a humanitarian, great young American, idealistic, young girl,” said O’Brien.

“One of the things that General [Mark A.] Milley, the chairman of the Joint Chiefs of Staff, did was name the operation that took down al-Baghdadi after Kayla Mueller, after what she had suffered. And that was something that people should know,” he said.

Mueller, a native of Prescott, Arizona, was kidnapped while doing humanitarian work in Syria in 2013. She was 26 years old when she was killed in 2015.

Mueller was traveling in the company of Syrian contractors for Doctors Without Borders (widely known as MSF, the acronym for its name in French), on the way back to Turkey after installing communications equipment at a hospital, when she was stopped on the road by a group of armed ISIS fighters. The others taken prisoner with Mueller were released over the next few weeks, but ISIS accused her of being a spy and kept her captive in various locations until her death.

There was some controversy early in Mueller’s ordeal when her family accused MSF of withholding an email address provided by her captors to begin negotiations for recovering her. MSF said it was unaware she accompanied its employees to Syria and would not have approved of her trip due to the high risk of kidnapping. MSF apologized and admitted it deliberately withheld the email address from Mueller’s family because it feared they could have endangered other hostages if they directly communicated with the Islamic State.

The Syrian MSF contractor Mueller was traveling with reportedly attempted to rescue her by approaching Islamic State representatives and claiming to be her husband, but Mueller refused to go along with the ploy because she had already told her captors she was unmarried and she feared they would kill her for lying to them.

“They’re a fabulous organization. They do wonderful work, but somewhere in a boardroom they decided to leave our daughter there to be tortured and raped,” Mueller’s father Carl said of MSF in 2016.

Mueller was held for a time by Islamic State financier Abu Sayyaf and his wife Umm Sayyaf. Abu Sayyaf was killed in a 2015 raid, while Umm Sayyaf (real name Nasrin As’ad Ibrahim) was taken alive and charged by the FBI with imprisoning and torturing Mueller. According to the FBI affidavit, Mueller was personally raped by Abu Bakr al-Baghdadi while in the Sayyafs’ custody.

Baghdadi referred to Mueller on various occasions as his “property” and his “wife.”

Umm Sayyaf told American and Kurdish intelligence officials that Baghdadi personally took Mueller in a car with him to Raqqa, Syria, in late 2014. Mueller was killed in Raqqa a few months later.

“She was a lovely girl and I liked her. She was very respectful and I respected her. One thing I would say is she was very good at hiding her sadness and pain,” Umm Sayyaf said of Mueller in a June 2019 interview.

Mueller also spent some time in the hands of the four British ISIS recruits known as “The Beatles.” Their leader, Mohammed “Jihadi John” Emwadi, frequently paraded Mueller in front of other prisoners.

According to other prisoners, Mueller was forced to wear an Islamic headscarf, but refused repeated demands to renounce her Christian faith and become a Muslim. She was known to directly contradict Jihadi John’s claims that she had converted in front of other prisoners.

Those other prisoners described Mueller as a woman of remarkable courage and willpower, as she resisted constant torture, sleep deprivation, sensory deprivation, sexual assault, and slave labor. According to a Yazidi sex slave who was held along with Mueller by Abu and Umm Sayyaf, ISIS fighters tore Mueller’s fingernails out during the early days of her captivity. Mueller nevertheless risked the wrath of her captors on numerous occasions to help other prisoners.

Frida Saide, a female employee of MSF who spent some time imprisoned alongside Mueller at an abandoned oil refinery in Syria, described her as a “very good friend” who had “a strong faith that gave her a lot of strength.”

“She was always considerate of others, even though she herself was in a very difficult situation. She was always concerned for other prisoners. She never stopped being concerned for the Syrian population living through just horrible things in this war and still are. She never stopped caring for others,” Saide said.

Mueller wrote a letter to her family in the spring of 2014 in which she apologized for the suffering she had put them all through and spoke of the importance of her faith.

“I remember Mom always telling me that all in all, in the end the only one you really have is God,” she wrote. “I have come to a place in experience where, in every sense of the word, I have surrendered myself to our Creator because literally there was no one else. By God, and by your prayers, I have felt tenderly cradled in freefall.”

“I pray each day that if nothing else, you have felt a certain closeness and surrender to God as well, and have formed a bond of love and support amongst one another,” Mueller wrote to her family.

Mueller’s family was extremely critical of how the Obama administration handled their daughter’s captivity. “The president could have been a hero, but he chose not to,” Carl Mueller said of Barack Obama in 2016 when criticizing the former president for failing to make a promised charity donation in Kayla Mueller’s name.

The Muellers said the Obama White House threatened them with criminal prosecution when they attempted to negotiate a ransom with ISIS, a policy Obama later admitted was “totally unacceptable.”

The Mueller family said Obama “made the whole situation worse” by arranging a famously lopsided prisoner swap to secure the release of American deserter Sgt. Bowe Bergdahl from the Afghan Taliban because the deal inspired ISIS to increase its demands for releasing its own hostages. Carl Mueller said Obama’s eagerness to recover Bergdahl while refusing to allow a ransom to be paid for Kayla was “pretty hard to take.”

Obama was also criticized for delaying too long after receiving information about the location of Mueller and two other American hostages, James Foley and Steven Sotloff, before authorizing a rescue mission. When the mission was finally conducted almost a month later, the prisoners had been moved. Foley and Sotloff were later murdered by ISIS.

Kayla Mueller was killed in the city of Raqqa, the Syrian capital of the ISIS “caliphate,” in February 2015. The Islamic State claimed she was killed when Jordanian airstrikes caused the building she was held in to collapse, but the Jordanians strongly disputed these claims.

Jordan was attacking ISIS with particular ferocity at the time due to the hideous videotaped murder of captive pilot Mu’ath al-Kaseasbeh, who was burned alive in a cage. President Trump referenced this murder in his address on Sunday morning announcing the death of Baghdadi, saying, “The shocking publicized murder of a Jordanian pilot who was burned alive in a cage for all to see.”