Bainbo: The text as I have it says "*Ten* years ago...". That makes much more sense. The singer is remembering the incident from well after the war.

However, you are right that "World War I" would have been an anachronism even in 1924. The usual term for it at that time (if something more specific than "the war" was needed) was "the Great War". That wouldn't scan in the song, but any of a number of descriptive phrases would have done the job.

I also tend to agree that a common soldier would have been more likely to say "football" than "soccer". However, is it possible that he would have said "soccer" if he wanted for some reason to exclude the possibility of Rugby football ("rugger")?