One of the first waves of Allied soldiers were the Parachute regiment.
Their task was to destroy the German machine guns before the landing parties arrived on the beach.
Their secret weapon - a parachuting dog called Bing. His exploits have just been turned into a children's book.
At the start of the war Bing's owner - the apply named Betty Fetch - handed him over to the army as she didn't have the rations to feed him.
Bing underwent intensive training in how to jump from a plane and how to spot German soldiers.
Bing made more than a dozen jumps behind enemy lines. He was injured in a shell blast but survived until 1955. He's one of only two dogs to have received the PDSA dicken medal - the animal equivilent of the Victoria cross.
And it's hoped his story will inspire a new generation to learn about the war.
The book is written by retired para Gil Boyd - a self confessed eccentric who raised £100,000 for Great Ormond Street hospital back in the 80s and has designed a string of inventions including a dog mounted camera for search and rescue.
Dogs are still used today in war. Money raised by the book will go to supporting soldiers killed or injured in Afghanistan.