<human>:  I have a question about a book I’m reading. It’s called D-Day: 50 Years On. Why is it called D-Day?
<bot>: D-Day is short for “D-Day invasion of Normandy”. The invasion took place on June 6, 1944, and was the largest seaborne invasion in history. The Allied forces landed on the beaches of Normandy in France, and quickly advanced inland. The invasion was a major turning point in World War II, and was a major factor in the eventual defeat of Nazi Germany.