The actual murder is performed in the unflinching sunlight of the desert. (I thought more than once of the brutally clear morning of Sept. 11, 2001.) Because sound is difficult to capture on a windy expanse of arid land, the victim is wearing a lapel mike. Mr. Sotloff introduces himself in sober tones and begins to read a scripted statement off what seems to be a teleprompter.

The executioner is cocky and ruthless, seemingly eager to get to the task at hand. When he does attack his bound victim, only the beginning is shown and then there is a fade to black. Once the picture returns, the head of the victim is carefully arranged on the body, all the violence of the act displayed in a bloody tableau. There is another cutaway, and the next potential victim is shown with a warning that he may be next.

Image A screen grab taken from a video released by the Islamic State in Iraq and Syria. Credit... SITE Intelligence Group, via Agence France-Presse — Getty Images

“It is an interesting aesthetic choice not to show the actual beheading,” Alex Gibney, a documentary filmmaker, said. “I can’t be sure, but they seemed to dial it back just enough so that it would get passed around. In a way, it makes it all the more chilling, that it was so carefully stage-managed and edited to achieve the maximum impact.”

The act is shocking regardless of the context. Remember near the end of Season 1 of “Game of Thrones,” when Eddard Stark, a main character, was poised to lose his head? We expected an arrow to come in from stage right to save him, but it did not and the blade fell swiftly. The audacity of the scene was something people talked about for weeks afterward, and the show’s unflinching violence has been a core element of its escalating popularity.

And so it is in real life. Video beheadings are a triple death — murder and defilement in a public way — and YouTube becomes the pike on which the severed heads are displayed. The actual butchery of the act is minimized by strategic editing, which suggests that the video is not an attempt at leverage but a carefully produced infomercial about how gangster and merciless ISIS is. It is a kind of global invitation: Come for the jihad and stay for the killing.

Writing in The New Yorker, Dexter Filkins did a remarkable job explaining what takes place in the videos.