Thinking about the anniversary of the Normandy landings, I was struck that the terms D-Day and H-hour were used to denote the start time of all allied military operations. Are there any specific reasons why the term has stuck to the particular operation of the Normandy landings?
The Normandy landings were referred to as D-Day in the U.K. and U.S. press because on the day of the landings, and in the following weeks, the code name for the operation (Operation Overlord) was still secret. The press wanted to report that 'the attack' on the Axis powers had started, and used the standard term D-Day as there were no restrictions on the use of this term. As it was used at the time in the press, the term has stuck. For example, the newspaper front page: http://www.archives.com/genealogy/newspapers-d-day.html has the headline "D-Day Chronology" near bottom.
The D merely stands for Day; in French, it's referred to as "Jour J". The term is indeed used for other D-Days, just not in regular English conversation.
Quoting from "D-Day" on Wikipedia:
The terms D-Day and H-Hour are used for the day and hour on which a combat attack or operation is to be initiated. They designate the day and hour of the operation when the day and hour have not yet been determined, or where secrecy is essential. For a given operation, the same D-Day and H-Hour apply for all units participating in it. When used in combination with numbers, and plus or minus signs, these terms indicate the point of time preceding or following a specific action. Thus, H−3 means 3 hours before H-Hour, and D+3 means 3 days after D-Day.
The article continues, to mention that several other lanugages use the initial letter in a similar fashion:
- Hari H (Indonesian)
- Час Ч (Chas Ch, Russian)
- Dagen D (Swedish)
- Dan D (Slovenian)
- E eguna (Basque)
- Jour J (French)
- Lá L (Irish)
- Tag X (German, an exception)
- Ziua-Z (Romanian)
The article also links to "Military designation of days and hours", which has examples of other terms, just as F-Hour or O-Day.
D-Day was a watershed (though not necessarily decisive) event in World War II. It represented the counterinvasion of France, and a springboard for the a strike at the German heartland, thereby undoing Germany's "rise" in the 1940 Battle of France.
World War II is widely regarded as the greatest war in human history, not only compared to wars before, but to wars afterward. Certainly, everyone hopes that the scope and scale of World War II will never be exceeded.
In this context, D-Day means "THE Day" of THE greatest war in human history.