<P> Other days such as A-Day (Battle of Leyte), L - Day (Battle of Okinawa) etc. have different meanings for the military . </P> <P> Other languages have terms equivalent to D - Day such as "Hari H" (Indonesian), Час Ч (Russian), Dagen D (Swedish), Dan D (Slovenian), E eguna (Basque), Jour J (French), Lá L (Irish), Tag X (German), and Ziua - Z (Romanian). The initial D in D - Day has been given various meanings in the past, while more recently it has obtained the connotation of "Day" itself, thereby creating the phrase "Day - Day", or "Day of Days". </P> <P> The earliest use of these terms by the United States Army that the U.S. Army Center of Military History has been able to find was during World War I. In Field Order Number 9, First Army, American Expeditionary Forces, dated 7 September 1918: "The First Army will attack at H hour on D day with the object of forcing the evacuation of the St. Mihiel Salient ." </P> <P> D - Day for the invasion of Normandy by the Allies was originally set for June 5, 1944, but bad weather and heavy seas caused U.S. Army General Dwight David Eisenhower to delay until June 6 and that date has been popularly referred to ever since by the short title "D - Day". Because of the connotation with the invasion of Normandy, planners of later military operations sometimes avoided the term to prevent confusion . For example, Douglas MacArthur's invasion of Leyte began on "A-Day", and the invasion of Okinawa began on "L - Day". The Allies' proposed invasions of Japan would have begun on "X-Day" (on Kyūshū, scheduled for November 1945) and "Y - Day" (on Honshū, scheduled for March 1946). </P>

Where did the term d day come from