Running in Circles

There was once a tribe living in the time of Great Migrations. People organized by families, moving from one hunting ground to the next, stopping briefly to gather supplies, but then moving on, searching for their permanent homeland.
This was common, with many tribes in motion, competing for the very few resources available.
The one thing that was different about this particular tribe was in the organization of their movement.
The tribe had scouts sent ahead on the trail, which was normal. The tribe then followed in a loose formation that extended back for several miles, which was also normal. And they had a rear guard, guarding the rear, again perfectly normal.
What was unique is that this tribe also had a large party of men and women that ran around the main group that was moving. Running twice the speed of the people walking forward, then still running quite fast around the other side, completely encircling the tribe while they moved. This group of runners changed frequently, allowing all able members of the tribe to take part.
Seen from a distance it must have looked strange. Seen from the perspective of an enemy it was intimidating. Should someone be foolish enough to attack, there would be a large group of people coming to the rescue in a few short minutes.
And if there was a tribe that discounted this, there was another surprise. All that extra running gave the tribe great endurance and strength.
They could choose to fight and win, or they could simply run, and outrun. Far better to have a choice in order to survive.
Since I exist, I must have come from a tribe. I like the idea of coming from the runners.