Here is a terrific article on Combatives use in WW1. A really fun read.
What the article clearly demonstrates, much to the chagrin of those who dislike grappling, close quarters combat, even in a weapons bearing environment, is a necessary skill set. Check out this quote from someone who was actually there:
“After a bayonet attack in nine cases out of ten trench or open warfare the men grapple. The man who has never been there before doesn’t know what to do”