Blitz II is a massive World War II total conversion for C&C Generals: Zero Hour. You can fight as the Allies, Axis or the Soviets in the biggest World War II mod in existence.
A pretty accurate historic total conversion, unfortunately engine limitations make it extremely unwieldy. It's a way larger scale game, which means units are way smaller, you control way larger forces, and lack of interface customization means many actions take more effort to be made than they should. Also, due to the fact the mod is more realistic than anything, you shouldn't expect any extremely original tech beyond Sherman Calliopes or artillery that requires towing - most of the units are just different categories of tanks varying in their categories and stats. Also, some design decisions are questionable, such as Axis and Soviets having multiple different factory types producing different units yet looking pretty much identical, or Manhattan Project requiring a long sequence of researches that requires a lot of microing and doesn't seem very worth it as you'll most likely will already have defeated the enemy by time they're all done.