Over the weekend, in the city of Louisville in Kentucky, different groups collided in a chaotic display of non-state armed power.

Strikingly, the police, the National Guard and civic leaders were nowhere to be seen for several hours. In other words, the competing militias had the run of a major American city.

It was like a scene from the Wild West, but without a sheriff in town. One militia leader is Dylan Stevens, known as the Angry Viking. He sees himself as filling a security vacuum following a summer of protests and of sporadic violence in a number of US cities.