By June 1914, the prototype M-Gerät howitzers had returned to Essen for final adjustments and would have been formed into a reserve artillery battery on completion in October.
On 2 August 1914, they were organised into KMK Battery 3 and sent to the Western Front with 240 men.
On 4 August, the German 1st Army arrived near Liège, the first target of the Schlieffen Plan, and began the Battle of Liège.
Although German troops entered the city on 7 August, its forts were firing upon the road to be taken by the 2nd Army and had to be reduced.
Heavy artillery began their attack on 8 August.
KMK Battery 3 was the first siege battery sent into battle to bombard the Fort de Pontisse on 12 August, which surrendered after two days.
The battery next moved to the Fort de Liers but the fort surrendered as the battery was emplacing.
KMK Battery 3 relocated to the Fort de Loncin, where Gérard Leman directed the defence of Liège.
Firing commenced on 15 August and lasted two hours, as the 25th shot fired struck a magazine, destroying the fort in the ensuing explosion.
The Germans carried Leman, unconscious, out of Loncin, and the last two forts, Hollogne and Flémalle, capitulated on 16 August.

With Liège captured, the 1st Army continued northwest while the 2nd and 3rd Armies marched to Namur, whose forts were undermanned, unmaintained, and poorly stocked with ammunition.
The 2nd Army arrived on 20 August 1914 to open the Siege of Namur, but began their main attacks the following day with 400 pieces of artillery.
KMK Battery 3 fired upon the Fort de Marchovelette, which was destroyed on 23 August by a magazine explosion.
The battery shifted its fire to the Fort de Maizeret, already under attack by four Austro-Hungarian Skoda 30.5 cm guns, and compelled its surrender.
With the eastern forts occupied, the Germans entered Namur itself and the remaining Belgian forces evacuated from the city.

Following the defeat of the Western Allies at Charleroi and at Mons, the British Expeditionary Force withdrew past Maubeuge, their base of operations after arriving in France.
On 24 August 1914, the advancing Germans arrived at the fortresses of Maubeuge and laid siege to its garrison of 45,000 soldiers.
The next day, the VII Reserve Corps were left behind the main German armies to take the city.
Bombardment of the forts began on 30 August, with KMK Battery 3 tasked with reducing Fort Sarts, but it mistakenly shelled an interval fortification in front of Sarts.
By 5 September, a hole in the fortress ring had been opened by German 21 cm guns, but they had by now exhausted their ammunition supply.
To widen that gap, the siege guns then expended their remaining ammunition against Forts Leveau, Héronfontaine, and Cerfontaine on 7 September, and destroyed them in quick succession.
The two remaining French forts surrendered that same day and the Germans occupied Maubeuge on 8 September.

With Maubeuge taken, German siege guns were available for an attack on Paris, but Germany's defeat at the Battle of the Marne blocked the advance of the 1st and 2nd Armies, and the guns were instead sent to Antwerp.
King Albert I had ordered a general retreat to Antwerp on 18 August, and his army arrived in the city two days later.
From Antwerp, Albert made attacks on the German flank on 24–25 August and 9 September, prompting General Alexander von Kluck of the 1st Army to send the III Reserve Corps to seize Antwerp.
It arrived and partially surrounded Antwerp from the southwest on September 27, and bombardment began the next day.
KMK Battery 3 arrived on 30 September and opened fire on the Fort de Lier, whose artillery narrowly missed the battery.
The fort was abandoned by its garrison on 2 October, allowing KMK Battery 3 to attack and destroy the Fort de Kessel in a single day.
The battery then moved to attack the Fort de Broechem, which was also destroyed within two days.
From 7–9 October, the Belgian army fled from Antwerp and the city surrendered on 10 October.

Early in 1916, all 42 cm guns were assigned to the 5th Army, which amassed a total of 24 siege guns, the highest con
By June 1914, the prototype M-Gerät howitzers had returned to Essen for final adjustments and would have been formed into a reserve artillery battery on completion in October. On 2 August 1914, they were organised into KMK Battery 3 and sent to the Western Front with 240 men. On 4 August, the German 1st Army arrived near Liège, the first target of the Schlieffen Plan, and began the Battle of Liège. Although German troops entered the city on 7 August, its forts were firing upon the road to be taken by the 2nd Army and had to be reduced. Heavy artillery began their attack on 8 August. KMK Battery 3 was the first siege battery sent into battle to bombard the Fort de Pontisse on 12 August, which surrendered after two days. The battery next moved to the Fort de Liers but the fort surrendered as the battery was emplacing. KMK Battery 3 relocated to the Fort de Loncin, where Gérard Leman directed the defence of Liège. Firing commenced on 15 August and lasted two hours, as the 25th shot fired struck a magazine, destroying the fort in the ensuing explosion. The Germans carried Leman, unconscious, out of Loncin, and the last two forts, Hollogne and Flémalle, capitulated on 16 August.
With Liège captured, the 1st Army continued northwest while the 2nd and 3rd Armies marched to Namur, whose forts were undermanned, unmaintained, and poorly stocked with ammunition. The 2nd Army arrived on 20 August 1914 to open the Siege of Namur, but began their main attacks the following day with 400 pieces of artillery. KMK Battery 3 fired upon the Fort de Marchovelette, which was destroyed on 23 August by a magazine explosion. The battery shifted its fire to the Fort de Maizeret, already under attack by four Austro-Hungarian Skoda 30.5 cm guns, and compelled its surrender. With the eastern forts occupied, the Germans entered Namur itself and the remaining Belgian forces evacuated from the city.
Following the defeat of the Western Allies at Charleroi and at Mons, the British Expeditionary Force withdrew past Maubeuge, their base of operations after arriving in France. On 24 August 1914, the advancing Germans arrived at the fortresses of Maubeuge and laid siege to its garrison of 45,000 soldiers. The next day, the VII Reserve Corps were left behind the main German armies to take the city. Bombardment of the forts began on 30 August, with KMK Battery 3 tasked with reducing Fort Sarts, but it mistakenly shelled an interval fortification in front of Sarts. By 5 September, a hole in the fortress ring had been opened by German 21 cm guns, but they had by now exhausted their ammunition supply. To widen that gap, the siege guns then expended their remaining ammunition against Forts Leveau, Héronfontaine, and Cerfontaine on 7 September, and destroyed them in quick succession. The two remaining French forts surrendered that same day and the Germans occupied Maubeuge on 8 September.
With Maubeuge taken, German siege guns were available for an attack on Paris, but Germany's defeat at the Battle of the Marne blocked the advance of the 1st and 2nd Armies, and the guns were instead sent to Antwerp. King Albert I had ordered a general retreat to Antwerp on 18 August, and his army arrived in the city two days later. From Antwerp, Albert made attacks on the German flank on 24–25 August and 9 September, prompting General Alexander von Kluck of the 1st Army to send the III Reserve Corps to seize Antwerp. It arrived and partially surrounded Antwerp from the southwest on September 27, and bombardment began the next day. KMK Battery 3 arrived on 30 September and opened fire on the Fort de Lier, whose artillery narrowly missed the battery. The fort was abandoned by its garrison on 2 October, allowing KMK Battery 3 to attack and destroy the Fort de Kessel in a single day. The battery then moved to attack the Fort de Broechem, which was also destroyed within two days. From 7–9 October, the Belgian army fled from Antwerp and the city surrendered on 10 October.
Early in 1916, all 42 cm guns were assigned to the 5th Army, which amassed a total of 24 siege guns, the highest con
Big Bertha (howitzer)