I had a lot of problems with this movie. There was a lot that was enjoyable, particularly in the visuals, but as with so many historical movies, it was both wrong and occasionally stupid wrong, as here. Let's dissect this scene.

First off, some of Jamukha's men are clearly shown to have lances in this scene. A lance is longer than a sword, particularly a sword held out to the side, and if any of the lancers had the presence of mind to simply point their lance at the sash dudes, they would have been taken down immediately.

But let's say the lancers are having an off day, and the sash guys break through. If we look at that 3rd screenshot, we clearly see that the sash guy is charging down an open lane in the formation of Jamukha's men, which happens to conveniently be just wide enough for the tips of those swords to slash the dudes on either side. But perhaps this is merely a clever tactic of Jamukha's whose importance will be revealed later.

Watching the scene, everyone who gets slashed by these guys seems to take the wound on the upper right side of their torso. Coincidentally, this happens to be where your arm usually goes, unless you are lifting it as high as possible in the air so that someone can slash your torso, as these men seem to be doing. All of the guys you see get cut are just waving their swords around high in the air- not trying to slash the sash guys, not trying to block the swords, just lifting their arms up and waiting for death.

Speaking of death, feel that area on the side of your torso and see how deep the ribs are. Not much, right? Do you think a cut there that was so shallow that it did not reach the ribs would be instantly fatal? Probably not. But maybe these sash guys have such strong wrists and sharp swords that they are simply cutting through several ribs a second at full gallop without apparent effort or strain.

Well, you may be asking, so if this scene is so wildly implausible, why is it in the movie? In the subtitles, Temujin mentions that he has his "strategy", which seems to be referring to the sash guys. The dude does have a reputation as a strategist to uphold, and the filmmakers had to portray that. Of course, they conveniently ignored all the real strategies and tactics used by the Mongols, such as feigned retreats, double envelopment, psychological warfare, deception tactics, human shields, etc., in favor of something that looked pretty cool and didn't require a lot of effort on their part.

So unless someone with more knowledge than me knows of some instance where this did occur, I think it's safe to say that this scene is Hollywood BS (well, it's a Russian movie, so... Rollywood?)