A Royal Marines' base in south-west England played a key role in the Allies' amphibious success on D-Day.
For the ambitious plans to pay off, the British government ordered practice to be undertaken close to home.
Instow in North Devon played host to the testing, from 1942.
Hardware was put through its paces on the sand, pebbles, rolling surf, steep gradients and mudflats - terrain which troops could have faced on Normandy's shoreline.
The base is still used today for trialling new equipment and testing Marines in amphibious skills.
Back in the day, the training was crucial, according to veteran landing craft Coxswain Clifford:
"If the Germans had have known what was going on here, they'd have blown it clean out of the ground."
Historian Tony Koorlander said working out how to disembark offshore, transport equipment on to the beach, and move troops quickly were "all things which they could develop and work on" at Instow.
Around their specialist training, the Royal Marines have made time to mark the 75th anniversary of D-Day in June.
A landing craft accompanied by serving commandos will travel to Arrowmanches as part of the commemorations.