In context, it was an astonishingly low casualty day. A few more than 4,000 deaths on the allied side out of roughly 150,000 combatants.
Compared with the Somme in WW1, in which there were somewhere between 50 and 60k of only British troops killed just on Day 1, and 1m dead and wounded during the entire battle.
D-Day was a triumph of planning, logistics and operational adaptation.
Visited Normandy a year ago. Amazed that the allies swept the Germans aside so quickly. Some places looked totally impregnable.