A group of cadets of the Ryazan Airborne School, by chance, end up, along with a small part of their territory, in medieval Rus' of the 13th century, at the time of the Mongol invasion. Using weapons from the 20th century and some other things that came with them, the cadets are trying to change the existing situation and protect the population from extermination. They also have to fight the tyranny of the princes, in such difficult times, continuing internecine wars. Having found an ally in the person of the Ryazan prince and, even using the location of Batu Khan himself, his wife and son, they repel the Catholic West, which is trying to enslave Orthodox Rus'. At the same time, they find themselves in various adventures, from which they emerge victorious.