World War VII

[Mike Weaver]

A curious question I'm confident one of you will be able to answer.  Here
follows a statement from the intro to a book,  Will Germany Crack,  by Paul
Hagen,  publ in US 1942,  UK 1943.

"...the last war (World War VII according to the now fashionable
nomenclature,  though it is probably hopeless to try to persuade most
Americans that it was not World War I.)"

Okay foax,   what were the first six and what was the criteria used? 
 I've got a bet with myself who will be first to answer it.  Will I win?

Easy as you go 

Mike