BRUSSELS (AP) — NATO Secretary-General Jens Stoltenberg is blaming a failure of Afghan leadership for the swift collapse of the country’s armed forces but says the alliance must also uncover flaws in its military training effort.

Stoltenberg says “the Afghan political leadership failed to stand up” and that “this failure of Afghan leadership led to the tragedy we are witnessing today.”

His remarks came after he chaired a meeting Tuesday of NATO envoys to discuss the security implications of the Taliban’s sweeping victory in Afghanistan in recent weeks.

NATO has been leading international security efforts in Afghanistan since 2003 but wound up combat operations in 2014 to focus on training the national security forces.

Referring to the way that the Afghan armed forces withered in the face of the Taliban offensive, Stoltenberg said that “was a surprise, the speed of the collapse and how quickly that happened.”

He says “there are lessons that need to be learned” at NATO.