Both Rob's and MtheGM's explanations sound plausible.

Whoever wrote the line would thus seem to have had some recruit experience and have beem writing specifically for a forces audience. Few others would have been likely to recognize either allusion. Perhaps the line - and the entire chorus except for "Bless" - was Godfrey's, and most or all of the remaining Prowse lyrics were added in 1940 to make an extended song of what had been previously just a rowdy chorus in the public domain. But I'm just thinking out loud.

Since my last posting in 2008, I've been watching for additional pre-1940 "Bless 'em All" information and have searched additional databases. Have found nothing new whatsoever.