How do upu compare Military Ranks in the US military with the German Military in Worls War 2?

You'll either have to obtain a book on them or search the websites. US ranks haven't changed much, so they'll be easy. You'll have to separate them into 3 general groups (for the main combatants): Officers, Warrant Officers, and Enlisted men. Enlisted men will contain two groups; NCOs and men (NCO=Sergeant).

If you include the navies of any of the combatants, you'll have even more details to be concerned about. Most navies don't use Generals; they use the term Admirals. They don't have 2nd Lieutenants either, they call them "Ensigns." Sergeants in the army are equal to about a "chief" in the navy; Seamen are called Privates in the army. A navy Captain is called a full bird Colonel in the US Army.

Recommendation: Get the US Army & US Navy down pat first; after you're familar with them, then move on to a foreign country's military.