D-Day Explained: The Normandy Landings of 6 June 1944

D-Day was 6 June 1944, when Allied forces landed by sea and air on an 80-kilometre stretch of the Normandy coast to open a front in western Europe. Wikipedia describes the landings — codenamed Operation Neptune, the assault phase of Operation Overlord — as "the largest seaborne invasion in history." By nightfall the Allies held five beachheads; by the end of June, 875,000 men had come ashore. The cost of the first day was at least 10,000 Allied casualties, with 4,414 confirmed dead.

Here is what happened, in the order it happened, and what the casualty figures do and do not tell us.

Why Normandy, and why 1944

Wikipedia records that Stalin had pressed for a second front since Germany invaded the Soviet Union in June 1941, but Churchill persuaded Roosevelt to postpone a cross-Channel invasion while the Allies fought in North Africa, Sicily and Italy. Planning for Overlord began in 1943, with General Dwight D. Eisenhower in command.

The planners, Wikipedia says, weighed four sites: Brittany, the Cotentin Peninsula, Normandy and the Pas-de-Calais. The two peninsulas were rejected because German forces could cut off an advance at a narrow neck of land. A large deception, Operation Bodyguard, and within it Operation Fortitude, used fake radio traffic and other misinformation to persuade the Germans that the main landing would come elsewhere. On the German side, Hitler gave Field Marshal Erwin Rommel command of the coastal defences of the Atlantic Wall — which, Wikipedia notes, Rommel reported shortly before D-Day was only 18% complete in some areas.

The background to the war itself is in the causes of World War II.

The weather decision of 4 June

The date was constrained by nature. Wikipedia explains that the planners wanted a full moon for the aircrews, and a landing shortly before dawn, midway between low and high tide with the tide coming in, so obstacles were visible and men spent as little time exposed as possible. Only a few days a month qualified. Eisenhower had chosen 5 June, but on 4 June high winds and heavy seas made it impossible to launch landing craft.

On the evening of 4 June, Group Captain James Stagg of the RAF forecast enough improvement for 6 June. The next suitable tides, without the full moon, would be 18–20 June. Eisenhower decided to go. Wikipedia adds the coda: a major storm battered the Normandy coast from 19 to 22 June, which would have made the later landing impossible. German forecasters, with less Atlantic data, predicted two weeks of storms, and several German commanders were away from their posts — Rommel among them.

The US Army's own history adds a human detail: Eisenhower expected casualties of up to 80% among the airborne forces, and went to an air base at Newbury to see off men of the 101st Airborne.

The night drop and the five beaches

The invasion began shortly after midnight. Wikipedia describes more than 2,200 bombers attacking the coast and about 24,000 American, British and Canadian airborne troops landing behind the beaches. The first action was the glider capture of the Caen canal and Orne river bridges at 00:16, taken intact. The US 82nd and 101st Airborne were badly scattered by cloud; the Army history notes that many were injured, killed or drowned in flooded lowlands, but that they fought on and caused confusion among German commanders.

Seaborne landings began around 06:30 on five sectors:

The times differed: Wikipedia notes the first landings on Gold were set for 07:25 because of tidal differences from the American beaches, and infantry on Sword began disembarking at 07:30. Strong winds pushed landing craft east of their targets, particularly at Utah and Omaha. At Utah, the 4th Division made significant progress inland and met the airborne troops. At Gold, Juno and Sword, fortified towns had to be cleared house by house.