The raising of ten new Siege Batteries of the Royal Garrison Artillery was authorised by Army Council Instruction 1091/1916, with effect from 22 May 1916.
| RGA Siege Battery | Raised at |
|---|---|
| 140 | Sheerness |
| 141 | Portsmouth |
| 142 | Tynemouth |
| 143 | Plymouth |
| 144 | Dover |
| 145 | Portland |
| 146 | Pembroke Dock |
| 147 | Portsmouth |
| 148 | Harwich |
| 149 | Hartlepool |
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.
Four officers and 78 men from the Hampshire, Essex and Durham RGA (Territorial Force) were to be allotted to 147, 148 and 149 Siege Batteries RGA respectively.