I give up!!
I am doing family research, and for days have been trying to pin down what war my great-grandfather was in, from the only picture I have of him. He is on horseback, and his horse and uniform give several clues but I can’t be sure.
I saw a thread on this board about Cavalrymen, so I was hoping someone might be able to help me identify any clues, etc., or at least direct me to a place that could help?
I can post a picture if anyone is good with this kind of thing …
Thanks in advance!!
Just a thought… If you know when your grandfather was born, then you should be able to work out an approximate date (given that your great-grandfather was most likely of military age around that time). If you can tell if he’s young or old in the picture, you could guess at the date even better.
Once you know the approximate date, you can consult the Timeline of United States Military Operations.
This site doesn’t allow photos to be posted, so you’ll have to put it on Flickr or Picasa or similar and post a link to it here…
The OP may have succumbed per his/her username by now, but just to keep it alive: guess who these obscure mounted troops were, without looking into the links:
One
Two
Three
Or you can scan through some Google images to see if any picture looks similar:
https://www.google.com/search?tbm=isch&q=mounted+calvary+horse
Two is wearing a U.S. Marines cap badge – and bears more than a slight resemblance to Joseph Gordon-Levitt. 
Any time you post the photo, someone will surely be by to help.
I believe Picture One is USCG beach patrol training.
No, not training future David Hasselhoffs, training guys to patrol long stretches of beaches to look out for submarine-borne saboteurs. Being on horseback let them cover a lot more beachfront than being on foot.
IIRC, one of the Operation Pastorius saboteurs was discovered by a USCG beach patrol.
I’d date the Marine to around 1920. The Coast Guard horsemen to 1940.
The Canadian (he has to be Canadian!) to around 1900. Is that really how the Mounties started out?!? 
That’s a Soviet war moose, which was given preliminary trials for use in the Winter War. The vestige of this program is a dairy producing therapeudic moose milk.