[Nogrod]

Yelling out aloud that the foe is not to pass serves multiple purposes, I think.

You can think of it as trying to intimidate the enemy.

You can think of it as stating your determination that you will rather die than let them pass.

You can think of it as a call to rally your troops around you.

And in all cases you can also see it as an incantation - in the supernatural sense, or just as giving a boost of morale to your troops, sharing the shared mission, or trying to weaken the opposition with a threat.