June 6, 1944 — better known as D-Day — was one of the most important days of the Second World War, when Britain, Canada, the United States and their Allies started the military push that would end in Adolf Hitler‘s defeat less than a year later.
Hitler’s forces had effectively conquered mainland Europe by the end of 1940, leaving the Allies with nothing but the island of Britain as a base. For the Allies, D-Day was about retaking territory on the mainland so they could fight a proper ground war with the Nazis.
The Allies stormed the beaches of Normandy, France in the world’s largest-ever amphibious invasion, braving heavy German resistance and sustaining thousands of casualties so they could gain a foothold on the edge of Nazi-controlled mainland Europe.
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That D-Day set the stage for many more “D-Days” to come, as the western Allies pushed Germany on one side while the U.S.S.R. waged a brutal campaign from the other.
The Allies’ success meant D-Day would forever be associated with the invasion of Normandy. Many have come up with meanings for that “D,” including “Day of Days” or “Doomsday.”
However, the actual meaning is more mundane.
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The Allies had code names for everything, and “D-Day” was commonly used to signal the first day of a secret attack. The “D” simply refers to the start day, and numbers are used to refer to what comes before and after. For example, the day before D-Day would be “D minus one,” and two days after would be “D plus two.” It’s essentially the same as the countdown for a rocket launch, when “T” is takeoff time and “minus” indicates the seconds before takeoff.
“The letters are derived from the words for which they stand,” according to the U.S. Army’s historical website.
In other words, the “D” in D-Day is a placeholder for “Day.”
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