What Is D-Day? A Guide to the Meaning and History

Have you ever heard of D-Day? It is a flag-flying holiday in the US that marks one of the most important dates in history. But what exactly is this holiday, and why do we celebrate it?

What is D-Day?

D-Day is a military term used to mark the start date of a combat operation, but it’s most famously associated with the Normandy Landings during World War II. On June 6, 1944, Allied forces launched Operation Overlord — a massive seaborne and airborne invasion aimed at liberating Western Europe from Nazi control. This marked the beginning of the end for Nazi Germany.

What Does D-Day Stand For?

D-Day isn’t an abbreviation for anything. Instead, it’s a NATO military term that refers to the day an attack is scheduled to begin. Related terms include E-Day, which means the day a NATO exercise takes place, or M-Day, when military mobilization begins. Since the term “D-Day” is now strongly associated with the Normandy landings, it is not often used by military planners anymore.

Where Was D-Day?

The Allies determined that the best way to enter Nazi-held Europe was by sea, which they had successfully done the previous year in Italy. Thus, the Allies chose to enter through northern France, which was across the channel from the Allies’ European base of England. This offered an opportunity to push the war front to Germany itself.

The Allies considered several sites along the coast of northern France; however, many had already been heavily fortified by the Nazis or had unfavorable locations. Normandy, a province in France located directly across the channel from England, had the best geography but didn’t have any easily accessible ports. The Allies decided to go ahead with the invasion on the beaches of Normandy anyway. Two portable harbors were constructed and towed from southern England into place during the invasion on D-Day to facilitate the landing of soldiers and supplies.

When Was D-Day?

D-Day took place on June 6, 1944. The first invasion started soon after midnight had passed, when aerial and naval forces bombarded Nazi defenses. Around 6 am, the Allies’ amphibious vehicles began to land on the coast, unloading thousands of soldiers onto the beaches of Normandy.

The Allies initially planned to invade on May 1. However, when Generals Dwight D. Eisenhower and Bernard Montgomery reviewed the plan, they insisted that additional forces were necessary. This meant procuring more amphibious landing craft, delaying the attack. They then set the date to June 5, which was postponed to the next day due to bad weather.

What Happened on D-Day?

Shortly after midnight on June 6, British, Canadian, and US aerial and naval forces began to bombard the Normandy coast, aiming for Nazi communication lines. At the same time, battleships started clearing the English Channel of mines to make way for the amphibious invasion. Around 6 am, bombardment moved further inland.

British and US aerial forces conducted airborne landings behind the beach, seizing bridges, railroad lines, and roads. At 6:30 am, US amphibious landing crafts and modified tanks that could function as boats began to land near the Utah and Omaha beaches. Many American troops waded through neck-deep water while under heavy fire to make it to land. British troops landed an hour later on the Gold and Sword beaches, taking control of the houses there that the Nazis had fortified. Meanwhile, Canadian forces landed at the Juno and Mike beaches.

In total, 156,000 Allied troops landed on June 6, and 875,000 joined the invasion throughout the month. Thousands of soldiers lost their lives on D-Day, but hundreds of thousands more pushed the war front across Europe to ultimately end World War II. The Normandy landings have often been called the beginning of the war's end in Europe.

How Long Did D-Day Last?

Fierce fighting continued throughout D-Day, as the Allied troops dug in and repelled counterattacks by the Nazis. Progress was slow, as exit points from the beaches were quickly congested and the beaches themselves were filled with damaged tanks and equipment. However, the Allied forces continued to push forward, creating a unified front across the various landing points on June 12. 

Over the following year, the Allies worked to liberate Europe from Nazi control, leading to Germany’s unconditional surrender on May 8, 1945.

D-Day as a Flag-Flying Holiday

D-Day is observed annually on June 6. Though it is not a federal holiday, many commemorate this day with memorials and ceremonies to remember the brave soldiers, many of whom were American, who liberated Europe. Some museums and war memorials host exhibitions featuring photos and films to pay tribute.

Americans are encouraged to observe this important day by proudly flying our US flags up high. In displaying the symbol of our freedom, we honor those who have fought and continue to fight for liberty and justice.