Early in 1916, all 42 cm guns were assigned to the 5th Army, which amassed a total of 24 siege guns, the highest concentration of them during the war. The Battle of Verdun was opened on 21 February 1916 with an intense, nine-hour long artillery barrage. The 42 cm guns were tasked with suppressing the artillery of Forts Vaux, Douaumont, Souville, and , but were unable to penetrate the concrete of the modern fortresses. On the second day of the battle, both of KMK Battery 7's M-Gerät guns were destroyed by premature detonations and KMK Batteries 5 and 6 both lost an M-Gerät each to the same cause. Most of the siege guns at Verdun were moved north in July to participate in the Battle of the Somme, and by September the only M-Gerät units left in Verdun were KMK Batteries 3 and 6.