World War II, analyzed!

I know very little about the War in the Air and would like to know more.
I would like to know who decided and why the RAF was to concentrate on night ops and the USAAF do the day-shift?
I see those methods extended to other theatres not just the Forces flying out of Britain.
A simple question but something I've often wondered about but never looked for an answer before.

I believe that the decision was made by the respective commanders.

Bomber Harris didn't want to risk his planes during day light, since they didn't have fighter cover until late in the war. And, carpet bombing didn't require accuracy anyway.

Spaatz however favored precision bombing which simply wasn't possible early on in the war during the night. He also was confident that the type or formation flying and the heavy (and abundent) armament of the B17 bombers would minimize losses.

Kris