The US military withdrawal from Afghanistan is now formally underway, according to the White House and several US defense officials. “A drawdown is underway,” White House deputy press secretary Karine Jean-Pierre told reporters aboard Air Force One Thursday. “While these actions will initially result in increased forces levels, we remain committed to having all of US military personnel out of Afghanistan by September 11, 2020.” Fewer than 100 troops, along with military equipment, have been moved largely by aircraft to execute President Joe Biden’s order to begin the withdrawal process no later than May 1, according to several US defense officials. In addition, contractors and US government workers are also departing the country, the officials said. The Pentagon has said it is concerned about personnel coming under attack from the Taliban as they depart so it’s not clear if it will disclose all the details of the departure process, which is due to be completed by September 11. There have been about 2,500 US troops in Afghanistan that are openly acknowledged, plus several hundred additional special operations forces. All of them will depart under the President’s orders. Chairman of the Joint Chiefs of Staff Gen. Mark Milley called the withdrawal “a complex operation and not without risk,” in a statement to CNN. “We have begun a deliberate coordinated responsible retrograde of US military personnel from Afghanistan. This is a complex operation and not without risk. And it will unfold over the coming weeks,” he added. A NATO official told CNN that NATO allies have also begun withdrawing troops and that they plan to have their exit “completed within a few months.” The official said they “will not go into operational details, including troop numbers or timelines for individual nations” to ensure their troops’ safety and that “any Taliban attacks during the withdrawal will be met with a forceful response.” Milley spoke with his NATO counterparts Thursday to ensure a coordinated drawdown, a defense official told CNN, stressing the organized, deliberate withdrawal of US and coalition forces from Afghanistan under the promise of “in together, out together.” Biden announced his decision earlier this month to end America’s longest war, saying that the US “went to war with clear goals” and has “achieved those objectives.” The deadline the President has set for troops to withdraw is absolute, with no potential for an extension based on worsening conditions on the ground. “The President’s intent is clear, the US military departure from Afghanistan will not be rushed. … It will be delivered and conducted in a safe and responsible manner that ensures the protection of our forces,” Jean-Pierre added. While Biden argued that the decades-long conflict no longer aligns with American priorities, lawmakers from both parties have expressed concerns that the US withdrawal will lead to a Taliban resurgence, reverse gains made by Afghan women and civil society, and endanger American hostages in the country and Afghans who worked with US forces. The military is wary of a worst-case scenario that would include a collapse of Afghan security forces and watching closely for any signs that it may be playing out on the ground. The threat is not only from the Taliban, which has threatened to attack US forces come Saturday, but also from guerrilla factions with their own agenda and priorities, a considerable risk in a country as disparate and fragmented as Afghanistan, a defense official said. Biden: ‘Afghanistan was never meant to be a multi-generational undertaking’ In his first address to a joint session of Congress Wednesday night, Biden argued that “war in Afghanistan was never meant to be a multi-generational undertaking of nation-building.” “We went to Afghanistan to get terrorists – the terrorists who attacked us on 9/11 – and we said we would follow Osama bin Laden to the gates of hell to do it. … And we delivered justice to bin Laden. We degraded the terrorist threat of al Qaeda in Afghanistan. And after 20 years of value – valor and sacrifice, it’s time to bring those troops home,” the President said. CNN reported last week that military equipment has been flown out of the country in recent days. A key calculation will be when to draw down so-called “rolling stock,” including armored vehicles that allow forces to move around. The Pentagon has assembled a significant protection force to send the Taliban a strong message that it is ready to respond if they attack US forces on their way out. Approximately another 650 ground forces, mainly Army Rangers, are headed into Afghanistan in the coming days as a covering force to protect troops as they withdraw, especially from remote areas. The US is also sending in additional Army artillery and rocket systems for force protection. The aircraft carrier USS Dwight D. Eisenhower will remain in the North Arabian Sea to conduct airstrikes against the Taliban if needed. And the Air Force has also positioned several B-52 bombers in the Gulf region. On Sunday, Gen. Austin Scott Miller, commander of US Forces Afghanistan and NATO’s Resolute Support Mission, said some troops were being moved within the country. “All of our forces are now preparing to retrograde. Officially the notification date will be the first of May, but at the same time as we start taking local actions we have already begun that,” Miller told reporters when asked at a news conference in Kabul if the American withdrawal from bases had begun. Officials have told CNN that after the withdrawal begins, there will be an effort to move conventional forces and equipment out as quickly as possible if that equipment is not turned over to Afghan forces or destroyed in place. US intends to maintain military influence when troops are gone Last week, the senior US general responsible for US troops in the Middle East made clear that the US intends to maintain military influence and the ability to carry out air strikes in Afghanistan after American and NATO troops are withdrawn. Gen. Frank McKenzie, the commander of US Central Command, which includes the Middle East and Afghanistan, told the Senate Armed Services Committee that military planners are looking at ways to continue operations in the country following the withdrawal. He said the US wants to be able to conduct counter-terrorism missions, at least from the air through the use of manned and unmanned aircraft, as well as carry out surveillance and reconnaissance. “We will have an architecture in the theater that will allow us to look into Afghanistan,” McKenzie said. “It will not give us the same picture that we have now. It will allow us to see in. The ranges will be greater, the resources will be greater, the risks will all be greater, but it will be possible to do those again. It is certainly not impossible, but we won’t have the vision we have now.” As the US prepares to fully withdraw its troops, the State Department on Tuesday ordered US government employees “whose functions can be performed elsewhere” to depart the US Embassy in Kabul. A State Department spokesman told CNN that by minimizing the number of its employees, “personnel who are urgently needed to address issues related to the drawdown of US forces and to continue the vital work we are doing in support of Afghanistan and its people will be able to remain in place.” Secretary of State Tony Blinken told CNN’s Jake Tapper in an interview Tuesday that even as the US is extracting its troops, “we are not disengaging from Afghanistan, we’re remaining deeply engaged in the diplomacy in support for the Afghan government and its people, development, economic assistance humanitarian assistance, support for the security forces.” This story has been updated with additional reporting.