What other info do you have about him? If you haven't tried Ancestry.com yet. I'd go there. They have a number of Kotora's in the military section.

If you can find him on the ship passenger list for his emigration you will often find an origin town in Czechoslovakia. All of my grandparents and their siblings who came over after 1900 have theirs clearly marked on theirs.

You want to check both sides of the voyage as well - almost without fail all of my family leaving Czechoslovakia sailed out of Bremen and into either New York or Baltimore. (On my wife's great grandfather's record leaving Bremen I also discovered his father's name as nearest contact back home.)

Of course, if you can find his US Naturalization documents they should have some good info as well - especially the Declaration of Intention and Petition for Naturalization.

If he did sail into NY, to help with finding him on the voyage I'd suggest using the forms on the Stevemorse.org site - you can try different info you do have in different ways using the Ellis Island Gold Form, for example.

http://www.stevemorse.org/

Here's a search for Kotora using the gold form: http://bit.ly/a8GZ8B

Also, if you don't find his crossing documents for some reason (it happens) don't forget to look for any others from his family that may have came over - they may have the origin town as well!

Finally - you may be able to request his military service records at NARA.gov - see their site for what's available and what you may be able to ask for:

http://www.archives.gov/genealogy/