As I read through the answer key for the chapter 11 pre-test, I see that the answer key does not capitalize the Day in D-Day. Could you explain the reasoning for this? In all my research from websites, etc., I am seeing both D's being capitalized. In the Merriam Webster dictionary, D-day force is as I have just posted, but any other use is D-Day. Any help with this to explain better to my students would be greatly appreciated.