Blowing up the base was intended to ensure that any equipment or information left behind would not fall into the hands of the Taliban.

Eagle Base, first started early in the war at a former brick factory, had been used throughout the conflict. It grew from a small outpost to a sprawling center that was used to train the counterterrorism forces of Afghanistan’s intelligence agencies.

Those forces were some of the only ones to keep fighting as the government collapsed, according to current and former officials.

“They were an exceptional unit,” said Mick Mulroy, a former C.I.A. officer who served in Afghanistan. “They were one of the primary means the Afghan government has used to keep the Taliban at bay over the last 20 years. They were the last ones fighting, and they took heavy casualties.”