Batsugun is a form of judo competition, usually used for dan grading tournaments.
The players are divided in two groups, one of them wears “red” and the other one “white” team.
Then they start competing against each other.
No weight categories, only dan categories.
In order to be promoted to the next grade, one have to beat 3- 6 competitors in a row, depending on the format.
Some formats, runned directly by Kodokan, would also allow leg grabbing and a few more old school judo technics.
Here are some short videos of Batsugun grading tournament from last Sunday in Osaka.