I've rarely seen it referred to as "WW2", as opposed to "WWII", but apparently it's been in relatively rare but consistent use in English [1] for a long time.

I've rarely seen it referred to as "WW2", as opposed to "WWII", but apparently it's been in relatively rare but consistent use in English [1] for a long time. Tweaking the query reveals that it's relatively more common in British English than English overall, although "WWII" is more common there overall as well. 1. https://books.google.com/ngrams/graph?content=WWII%2CWW2%2CWWI%2CWW1&year_start=1930&year_end=2000&corpus=en-2019&smoothing=3 https://books.google.com/ngrams/graph?content=WWII%2CWW2%2CW... 2. https://books.google.com/ngrams/graph?content=WWII%2CWW2%2CWWI%2CWW1&year_start=1930&year_end=2000&corpus=en-GB-2019&smoothing=3 https://books.google.com/ngrams/graph?content=WWII%2CWW2%2CW...