Valenki.

This is coolbert:

Here is the valenki boot. The boot as worn by Soviet troops in winter conditions. Made of FELT!
Wool is very worm EVEN WHEN WET!!

"traditional Russian winter footwear, essentially felt boots . . . Valenki are made of wool felt. They are not water-resistant, therefore they are sometimes worn with galoshes to protect the felt."

"Valenki are a part of the Russian army uniform in winter . . . both winter boots and valenki are worn in the Russian army and that valenki are generally preferred for lower temperatures."

There is a boot obtainable in the U.S., for outdoorsmen, that is rubber on the outside, with FELT inserts. Removeable inserts, several carried by the user, one drying while another being worn. Very warm in all temps!!

coolbert.