The invasion fleet was under radio silence to avoid enemy detection which led to the release of Gustav who flew 150 miles across the Channel to RAF Thorney Island near Chichester, West Sussex.
Within five hours and 16 minutes, the first message was received back to the UK that the Normandy landings had commenced.
Watch: the vital role of pigeons for British troops.
Richard Chambers, Development Officer at the Royal Pigeon Racing Association, has been in Normandy for the commemorations: “It has been incredible to recreate the iconic scene on Sword Beach 75 years on.
"Working with NATO’s Allied Rapid Reaction Corps we have been able to further commemorate and highlight the crucial role racing pigeons played in wartime.
"Our pigeon will be flying 145 miles back to its home in Portsmouth which it will complete in around three and a half hours.”
Many pigeons air dropped in parachute cages to the pigeoneers signallers in the field. The pigeons would be placed into a cardboard container which was strapped to a parachute.