KABUL, Afghanistan — Taliban fighters posed for the camera, their shawls and bandannas covering their identities but not their jubilation, as they captured the main roundabout in the northern Afghan city of Kunduz early this month in what could have been called “operation hoist the flag and pull out a smartphone.”

The shaky cellphone video directly contradicted Afghan and American military spokesmen, who were promising that Kunduz was safe from falling for a second time in one year. During the invasion, insurgents live-tweeted their victory and flooded social media with videos, often shot by fighters narrating their movements in close to real time. In the video from the roundabout, one of the many fighters in the background is heard saying into a phone: “I will call you back. The flag is going up. I have to film it.”

It was not an isolated incident. When the Afghan government said the insurgents were far from the southern provincial capital of Lashkar Gah, the Taliban quickly put out a video showing a fighter driving around the city’s outskirts in a seized government Humvee, steering wheel in one hand and microphone in the other.