Another uniform to identify...

Here’s a picture of a German WW2 veteran’s private photo album.
What kind of uniform would that be?
Maybe a Polish cavalryman in a fine mood although becoming a POW?

The hat would suggest Polish, could it be Rumanian possibly?

The cap and collar tabs definitely strike me as Polish.

It’s definitely polish. I’ll try to find out what unit it was.

Not trying to be funny, but what is the historical derivation of what looks like a paper bag blossoming out of the top of a military cap?

Is there some earlier type of cavalry or other headgear that it is derived from?

That’s no bag, it’s a huge wooden mallet wielded by the guy behind. Another ww2 comedy moment.