The loss of the armored cruiser Blücher during the Battle of Dogger Bank in January 1915 rendered its four reserve 21 cm SK L/45 C/06 guns surplus as no other ships used them.

It rotated on a pivot at the front of the mount and the rear was supported by rollers resting on a semicircular rail and was generally equipped with a gun shield.

[1] One obvious change made for land service was the placement of a small counterweight just forward of the trunnions to counteract the preponderance of weight towards the breech.

The early loss of three out of four armored cruisers of the Prinz Adalbert and Roon classes to mines and submarines made their reserve guns available as well.

Seven cars could carry a portable metal firing platform (Bettungslafette) that had a central pivot mount and an outer rail.

It was assembled with the aid of a derrick or crane, which took between three and five days, and railroad tracks were laid slightly past the firing platform to accommodate the front bogies of the gun.

After the gun's pintle was bolted to the firing platform's pivot mount, the entire carriage was jacked up so that the trucks and their sections of rail could be removed.

One SK L/40 in Bettungsschiessgerüst was sent to reinforce the defenses of Gallipoli in 1917 and remained there for the rest of the war under the command of Kommando FR 17.

Two "Peter Adalbert" in Bettungsschiessgerüst participated in the Battle of Passchendaele in July 1917 and two were stationed opposite Verdun in August 1917.

Four others escaped destruction by the Military Inter-Allied Commission of Control because they were assigned to Batterie Plantagen on coast defense duties at Swinemünde.