Hello
Sorry for answering so late.
According to the military regulations, it was supposed to have a helmet (helmet) on the head in the ranks (parade, celebration or general battle). So it was with Alma. But later it was revealed that it is not convenient. When heated (the helmet was krzhany) it decreased in size.
Caps are provided for being out of order and were not introduced by the mouth. They were sewn from overcoats that had served their time (a new overcoat was issued every three years). After Alma, caps were worn as a rule. It was simply more convenient, but if you showed up in St. Petersburg in a cap, you would have received a penalty.