KABUL, AFGHANISTAN—In what officials said was the "only way" to move on from what has become a "sad and unpleasant" situation, all 100,000 U.S. military and intelligence personnel crept out of their barracks in the dead of night Sunday and quietly slipped out of Afghanistan.

U.S. commanders explained their sudden pullout in a short, handwritten note left behind at Bagram Airfield, their largest base of operations in the country.

"By the time you read this, we will be gone," the note to the nation of Afghanistan read in part. "We regret any pain this may cause you, but this was something we needed to do. We couldn't go on like this forever."

"We still care about you very much, but, in the end, we feel this is for the best," the note continued. "Please, just know that we are truly sorry and that we wish you all the greatest of happiness in the future."

According to firsthand accounts, the 90,000 American troops stationed in Afghanistan lay in their beds pretending to be asleep until well after midnight Tuesday. They then reportedly tiptoed out to a fleet of awaiting Humvees, tanks, armored cars, and stealth aircraft; gently eased the doors shut; and departed as silently as possible so as not to wake the 30- million-person nation.

Gen. David Petraeus, outgoing commander of U.S. forces in Afghanistan, acknowledged that while finally leaving Afghanistan the way they did was perhaps not the "most ideal" way of ending things, emotions in the region had been running too high lately to consider any other alternative.

"We could have slowly and steadily withdrawn from Afghanistan, but trust me, that would have needlessly prolonged what we both knew deep down was an unhealthy, dead-end relationship," Petraeus said. "And we just couldn't bear to look the Afghan people in the eye and tell them flat out that we were packing up and leaving."

"So we decided to sneak out the back through Tajikistan while the country was asleep," Petraeus added. "We're not proud of it, but it was the least painful option for everyone."

According to Pentagon sources, years of growing resentment, deep-seated trust issues, and periods of outright hostility had taken their toll on the relationship, leaving both partners hardened and bitter. After reportedly taking a "long look in the mirror" last week, senior defense officials came to the conclusion that they had "wasted a decade of [their] lives" with Afghanistan, prompting them to finally seek an end to their dysfunctional and destructive long-term engagement.

"When we went into this, everything seemed so perfect—that first democratic election in 2004, Operation Anaconda—those were great times," said Gen. James Mattis of U.S. Central Command, who stated that he would always cherish the warm memory of their early days together in Mazar-i-Sharif. "But we've grown so far apart since then. Sometimes it's hard to remember why we even got involved in the first place."

Despite walking out on Afghanistan, Mattis made it clear that the U.S. still cared deeply about the country and always would. He assured the war-torn nation Americans would never forget about them and promised the U.S. would send several hundred million dollars back to Kabul from time to time to make sure they were getting along okay.

Thus far, Afghans' reactions to the surprise withdrawal have been mixed. While many citizens expressed relief at the pullout, claiming the U.S. had "made [their] lives a living hell," they also admitted the departure had left them feeling deeply unstable and insecure.

"The U.S. told us they cared and that they had our best interests at heart, and I really thought this time might be different, but they were just as selfish as the Soviets and the British," said Pashtun tribal leader Ashraf Rahman Durrani, referring to Afghanistan's history of abusive relationships. "We're a strong, proud nation, though. We've been through a lot, and we'll find a way to get through this, too."

At press time, distraught American officials confirmed they had made a "terrible mistake" ever leaving Afghanistan, and were amassing troops at the border to reinvade the country by week's end.