The Merville Battery was composed of four 6-foot-thick steel-reinforced concrete gun casemates, each designed to protect First World War-vintage 100 mm guns. Other buildings on the site included a command bunker, accommodation, and ammunition magazines. During a visit on 6 March 1944 Field Marshal Rommel ordered the building to speed up, and by May 1944, the last two casemates were completed,
The battery was defended by a 20 mm anti-aircraft gun and several machine guns in 15 gun positions, all enclosed in an area 700 by 500 yards surrounded by two barbed wire obstacles 15 feet thick by 5 feet high, which also acted as the exterior border for a 100-yard-deep minefield.
Allied intelligence had judged from the size of the concrete gun emplacements that the guns must be around 150 mm in calibre and could threaten the British landings at Sword Beach, only 8 miles away.
D-Day - 6th June 1944
The British 9th Parachute Battalion, part of the 6th Airborne Division, was given the objective of destroying the battery on D-Day itself. But their parachute descent was dispersed over a large area and gliders missed the LZ, so instead of over 600 men, only 150 with no heavy weapons or equipment arrived at the battalion assembly point. Regardless, they pressed home their attack and succeeded in capturing the battery, only to discover that the guns were vintage, without the range to trouble the landings. Using what explosives they had been able to recover, the surviving 75 men tried to disable the guns.
The 1st Special Service Brigade was tasked with linking up with the 6th Airborne Division on the eastern flank of Sword Beach and securing the high ground near La Plein. No. 3 Commando landed at La Breche, west of Ouistreham just after 9am, coming ashore in the second wave. They were engaged before they hit the beach, and three of the landing craft that the commandos were travelling in were hit by high-velocity shells. Casualties were high, with No. 6 Troop suffering at least 20 wounded, but in the end they were lower than had been expected.
However, later in the afternoon, once the paratroopers had withdrawn, two of the guns were put back into action by the Germans who had been sheltering undiscovered in the bunkers.
D-Day +1 – 7th June 1944
On the morning of 7th June, as the 9th Battalion were heading to Le Plain on their next phase, artillery shell began to fall on the beach at Ouistreham Riva-Bella, Sword Beach. The British Headquarters thought that this could come only from the Merville battery, and ordered a second attack.
A combined force from Nos. 4 and 5 Troops of No 3 Commando carried out an attack at midday. Approaching from the south, No. 4 Troop moved across the open ground before taking up position behind the hedgerows 300 yards from the battery and from where laid down covering fire for No. 5 Troop which approached from the east with fixed bayonets. After a stubborn defence, in which a number of Commandos were killed, they took the battery. However, shortly afterwards they were counterattacked by German force supported by self-propelled artillery. Eventually the Commandos were forced to withdraw back to La Plein.
Following this the unit became involved in largely defensive operations as the 1st Special Service Brigade dug in. Nevertheless they kept up the pressure on the Germans by carrying out offensive patrols, small scale raids and sniping.
