StP Mont De La Motte H.K.B.

StP Mont De La Motte H.K.B. Batterie 5./H.K.A.B. 1245.

3 x (under construction) R688.

3 x 17cm K18 guns.

1 x 10cm le.F.H.14/19(t).

1 x 2cm Flak 30.

1 x 2cm Flak 38 Vierling (four barrel).

3 x R688 casemate under construction, it looks as though only the foundations had started to be dug.

R688 at Etaples les Trembles H.K.B 1944/45.

R688 at Etaples les Trembles H.K.B.
John being used for perspective. Showing the size of these bunkers.

17cm K18 gun.
As you can see a very heavy gun, it can be fired on a turntable or on its carriage (Lafette). It took a large crew and needed a heavy towing tractor to pull it. The only problem was the time to assemble and disassembled, it took too long and many were left behind as the Germans retreated through France.
17 cm Kanone 18 in Mörserlafette.
abbreviated as 17 cm K 18 in MrsLaf.
Wiki.