The First World War is English, but WWI is American

According to the Oxford Canadian Dictionary (2001), the entry “First World War” equates with “World War One”.  But in separate entries it also describes “WWI” and “WWII” as North American terms.  If we look to Churchill, or, rather, to books about him, both Roy Jenkins’ Churchill (2001) and Martin Gilbert’s The Power of Words (2012) have index entries for “First World War” and “Second World War” – yet none for “World War One” or “WWI”, etc. 

Looking at my Canadian undergraduate academic transcript at Trent University, the course I took was listed as the “First World War” – as taught by an Oxford-trained historian who published a book called The First World War.  In other words, for purists the “First World War” is considered English/Canadian.  The one exception I can find is The History Today Companion to British History (1995), perhaps because the magazine itself caters to more popular tastes.

Similarly, French and German does not have an equivalent “World War One” or a “World War Two”.  Instead there is Première Guerre mondiale and Erster Weltkrieg, etc. 

Thus, it is an American tradition of orthographic simplification that abbreviates these events as “WWI” and “WWII”.  Consider other examples from American industry such as iPhone3, or Xbox5, and Windows 11.