Sarn

It old traditions in the holiday of the Spring coming(Maslenitsa). It solves problem with the guy like in the first post. Who wants to go and fight with guys who want fight too

The "wall-on-wall" fight (with anywhere from dozen to several hundreds participants) was performed strictly by rules and could go on for hours. Both "walls" had a chief fighter, who served as a tactician and a commanding officer. "Walls" themselves were tight straight formations 3-4 ranks deep. Repeated attacks were performed, aiming to push the opposing "wall" out of the game area. Basic tactics were used, such as breaching using heavy fighters (who were usually held in reserve), encircling, false retreat and others; but as a rule, tight wall formation never broke. Tactics also included battle planning. The "wall-on-wall" fights, while performed for entertainment, were in fact close to military training. For example, notable ethnographer V. Gilyarovsky recalled that during his voluntary service in an infantry regiment soldiers often staged wall-on-wall fistfights with factory workers.

A famous phrase in Russian, "Do not hit a man when he's down", has roots in that sport
https://en.wikipedia.org/wiki/Russian_boxing