

You’re tripping yourself up on the difference between British English and American English. Canadian English is tolerant of both forms.
Oxford, where he wrote his thesis, would require ‘an’ before ‘historic’. When Governor of Bank of England, he would have had to have been careful to use British English.
If you’re a Canadian using American spelling and grammar checkers to define your language, you might wish to reconsider that. MS Word does have Canadian and UK English options.
Can we talk about deaths per capita and military and civilians contributing to war effort per capita for a country that was NOT itself attacked?
Yes, there were U-Boats attacking merchant marines on the east coast and Japanese balloons flying in on the west. But the societal contribution to a war not in our soil was and is astonishing.