US President Joe Biden on Monday blamed the Afghan leadership for the Taliban takeover and firmly defended his decision to pull out troops from the war-torn country.

In his address to the nation, Biden said that the rapid end of the Afghanistan government only vindicated his decision, noting how the Afghan army surrendered to the Taliban.

“American troops cannot and should not be fighting the war, and dying in a war that Afghan forces are not willing to fight for themselves,” Biden said.

“I stand squarely behind my decision. After 20 years, I’ve learned the hard way that there was never a good time to withdraw US forces,” Biden told the nation.

Biden is the fourth President of the United States to be at war in Afghanistan and had insisted he would not hand America’s longest war to his successor. But he is under pressure to explain how security in Afghanistan unraveled so quickly, especially since he and others in the administration had insisted it wouldn’t happen, the Associated Press reported.

Most Republican leaders have not pushed the Biden administration to keep troops in Afghanistan over the long term. His predecessor Donald Trump had also pushed to exit the country. Still, some in the GOP stepped up their critique of Biden’s withdrawal strategy and said images from Sunday of American helicopters circling the US Embassy in Kabul evoked the humiliating departure of US personnel from Vietnam.