▶ Watch Video: Security threats plague final hours as president’s deadline for U.S. Troops leaving Afghanistan arrives Doha, Qatar — The Taliban was in firm control of Kabul’s international airport on Tuesday morning, hours after the last U.S. military plane took off officially ending America’s longest-ever war. But the fate of dozens of American citizens, and many more Afghans who helped the U.S. and its allies, was uncertain after they were left behind by a chaotic evacuation effort. CBS News correspondent Charlie D’Agata was in Qatar on Tuesday, which has become the new home of the U.S. Embassy that was forced to evacuate from Kabul. On Monday night, the last U.S. mass-evacuation flights landed at America’s sprawling al-Udeid Air Base in Qatar. Then came some of the last American troops to get out of Afghanistan. D’Agata said the last U.S. plane left almost at the stroke of midnight in Kabul. With its departure, the U.S. handed the country back to an enemy it spent 20 years fighting. Defensive flares lit up the sky in Kabul as the last American C-17’s flew out of the Afghan capital, for good. U.S. troop withdrawal ends 20-year Afghan War… 01:44 Moments later, celebratory Taliban gunfire rang out across the city, lighting up the night sky with tracer fire almost like fireworks. By Tuesday morning the Taliban were out in force, not only on the streets and at Kabul’s airport, but in videos online, making it clear that the country was under new management. Videos showed gunmen strolling through the airport, posing with some of the disabled military equipment left behind. Taliban fighters sit in the cockpit of an Afghan Air Force aircraft at the airport in Kabul on August 31, 2021, after the U.S. pulled all its troops out of the country to end a brutal 20-year war – one that started and ended with the Taliban in power.WAKIL KOHSAR/AFP/Getty Taliban spokesman Mohammed Naeem posted a video message online Tuesday congratulating the group’s fighters and calling their victory “the result of 20 years of our historic sacrifices.” He had special praise for the group’s suicide bombers. “We left a historic chapter behind,” said Naeem. “The coming chapter is important, it is an uprising for an Islamic system, and we pray to Allah to give us strength to provide an Islamic system for the people of Afghanistan to live in peace.” America’s longest war came to an end with a chaotic, calamitous mass evacuation, and a suicide bombing by the ISIS faction in Afghanistan that cost the lives of 13 U.S. servicemembers and 170 Afghan citizens. Taliban fighters stand guard near an Afghan Air Force aircraft at the airport in Kabul, Afghanistan, August 31, 2021, after the U.S. pulled all of its troops out of the country.WAKIL KOHSAR/AFP/Getty Flights in and out of Kabul’s airport have stopped, stranding an unknown number of Afghans who wanted to flee Taliban rule, including many who helped the U.S. and its allies during the two-decade war effort. Some of those lucky enough to escape wound up at the al-Udeid base in Doha. In two weeks, hangars there were transformed into holding areas for 55,000 Afghan refugees. “Wherever they say for our journey, we will go,” said one evacuee, grateful just to be out of Afghanistan. Remaining Americans, and Afghans holding special visas, now have limited options: They must either catch a bus and head for the border, hoping to flee into a neighboring country like Iran or Pakistan; wait at the airport in hopes of flights resuming soon; or simply go home and hunker down. Whatever they decide to do, they’re left to hope that the Taliban make good on their promises not to prevent people from leaving the country, and not to seek revenge against anyone who helped foreign forces over the last 20 years. U.S. completes Afghanistan withdrawal 12:34 The U.S. nationals and their allies will also be hoping that America still holds some degree of influence over an enemy it was unable to defeat. “A new chapter of America’s engagement with Afghanistan has begun,” declared Secretary of State Antony Blinken on Monday. “It’s one in which we will lead with our diplomacy. The military mission is over, a new diplomatic mission has begun.” Physically, that diplomatic mission will now operate out of Qatar, along with the U.S. Embassy that was uprooted from Kabul. Qatar is a major regional U.S. ally that has also served as the go-between with the Taliban. That role is only going to become more important in the future. The Taliban on Tuesday lauded countries that decided to keep their embassies and diplomats in place over the last couple of chaotic weeks, and it urged nations that did pull out to come back, as leaders of the group suggested work was well underway to establish a new government in Kabul. A spokesman said the Taliban would try to secure the international airport and get operations running again, but he and other leaders acknowledged that the former insurgency may need technical help to do that, and they were in talks with Turkey and Qatar about possible assistance.