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.