How did the Merville battery threaten Allied troops at Sword Beach?

The Merville battery posed a significant threat to Allied forces at Sword Beach because it was equipped with four large artillery guns housed in fortified concrete casemates. These guns were positioned to target the seaborne landing forces as they arrived on the coast.1

To neutralize this danger, the British 6th Airborne Division was tasked with destroying the battery as a primary objective of their D-Day operations. Despite a scattered parachute drop that left Lieutenant Colonel Terence Otway’s 9th Battalion with only 150 of its 750 men, the unit successfully captured the battery in a daring assault, effectively silencing the threat to the troops landing at Sword Beach.1