"the small group of men with yellow shakos"

 Shakos are a particular kind of peaked hat worn as part of military uniform. Tall, cylindrical, and oftened adorned with a feather, the high fronts offered a space for a badge or other embellishments. The hats originated with the Hungarian hussars in the 1700s, and spread to other countries as the hussars also spread.

See here for some wonderful Russian army hats, including a shako with an extraordinarily big feather on top.