Trump said at Saturday's Save America rally in Cullman that the world is now looking at Washington thinking: "What the hell happened so quickly to the United States of America?"
The former president said the situation in Afghanistan will go down as "one of the greatest embarrassments" and the "greatest foreign policy humiliation" in the history of the US.
Trump accused US President Joe Biden of surrendering the nation's military bases in Afghanistan, stressing that American troops are leaving $83 billion worth of military equipment behind.
"This will go down as one of the great military defeats of all time", Trump said, calling the troop withdrawal a "total surrender" and "gross incompetence by the nation's leader". Trump emphasised that under his presidency, this would never have happened.
About the president, his predecessor bitingly noted that "he was on vacation as Afghanistan was going to hell".
Trump suggested that Washington should have analysed the experience of Soviet forces in Afghanistan before taking any drastic steps. He called Biden's troop withdrawal from Afghanistan a "horrific decision", saying that the US should be prepared to send troops back into Afghanistan in order to help thousands of American citizens who remain there.
Trump said Biden's faulty approach to Afghanistan will result in "the Taliban* flag flying over our [US] embassy" in Afghanistan on September 11th, the 20th anniversary of the 9/11 attacks.
According to the former president, the right way to withdraw from the country was to pull out military personnel only after US citizens and valuable equipment had left the war-torn nation, then "you bomb the hell out of the bases", instead of leaving them for the Taliban to use.
Trump stressed that under his administration the US had reconstructed the army, but he regretfully stated that it had all "evaporated" and has now been handed over to the enemy.
"This was not a withdrawal, it was a total surrender", Trump concluded.
Violence had been on the rise in Afghanistan amid the withdrawal of international troops from the country. The United States began pulling its forces out of Afghanistan in May with the aim of removing all US troops by September 11th.
On 15 August, the Taliban entered the Afghan capital Kabul. Afghan President Ashraf Ghani resigned and fled the country to prevent what he described as bloodshed if the militants had to fight for the city. Most countries have since reduced or evacuated their diplomatic missions in Kabul.
The chief of the political office of the Taliban, Abdul Ghani Baradar, will likely make a decision concerning the structure of the future Afghan government over the next two weeks, a source in the Taliban told Sputnik on Saturday.
Taliban spokesman Suhail Shaheen said earlier this week that the United States must withdraw all troops from Afghanistan by 11 September.
* The Taliban is a terrorist organisation banned in Russia and many other nations.