First Appearance: Action Comics (vol. 1) #31 (Dec. 1940): "In the Grip of Morpheus"
Number of Appearances: 1
Worked for: Baron Munsdorf
Kolb is the chief henchman of this story's principal villain, Baron Munsdorf, who is apparently a loyal German Nazi "fifth columnist." The Baron is in the United States trying to obtain the formula for a powerful new anaesthetic gas invented by Professor Hunter of Brentville. Kolb is specifically identified by Professor Hunter as an agent for a foreign spy ring. For example, in panel 1 on page 10, Hunter tells Superman, "I hired Kolb as my assistant, not knowing that he was the agent of a spy ring out to get the formula of my new anaesthetic gas..."
From the context of the story, it is safe to assume that Kolb is German. This is never explicitly specified, however. Note that "Kolb" is indeed a German name. It is from the from Middle High German word kolbe.
Baron Munsdorf in this story is clearly a loyalist to his country. A man of means, the baron appears to engage in this story's spycraft out of an idealistic (or fanatical) support for his country. Kolb may be less of a "true believer." After all, he allowed his hired thugs to go "off script" and use the Professor Hunter's sleep gas to commit a bank robbery. But Kolb is probably a Nazi as well. Kolb may not be as much a "true believer" in the Nazi cause as his boss, but the baron probably would not have kept Kolb in such a prominent position in his spy ring if he doubted Kolb's loyalty to Nazism.
These Nazi connections and associations are inferred from the story's context and the milieu in which it was published. The word "Nazi" is never actually used. It was common for comics and popular media of the time to be very reticent to explicitly refer to Hitler or Nazism by name.
Prior to Baron Munsdorf and his henchman Kolb, some earlier Superman villains may have been inspired in part by Nazis and Fifth Columnists, but these two are the first Superman characters identifiable as actual Nazis.
Suggested links for further research about this character and the character's religious affiliation: