The raising of six new Siege Batteries of the Royal Garrison Artillery was authorised by Army Council Instruction 397/1916, with effect from 14 February 1916.
| RGA Siege Battery | Raised at |
|---|---|
| 108 Siege Battery | Forth Defences |
| 109 Siege Battery | Dover |
| 110 Siege Battery | Sheerness |
| 111 Siege Battery | Weymouth |
| 112 Siege Battery | Portsmouth |
| 113 Siege Battery | Pembroke Dock |
The ACI stated that the establishment of each battery would be that laid down for batteries equipped with 6, 8 or 9.2-inch howitzers.
Three officers and 78 men from the Forth, North Scottish and Clyde RGA (Territorial Force) were to be allotted to 108, 109 and 110 Siege Batteries RGA respectively.