Here is a terrific article on Combatives use in WW1. A really fun read.

http://www.bloodyelbow.com/2012/11/12/3614692/the-martial-chronicles-in-the-trenches

 

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”