The principle fire unit prior to 1898 was the Battery. At the end of the 19th century , the improved command and control of Artillery, particularly to allow greater concentration was seen as being vital to the effective tactical deployment of Artillery. General Marshall's Committee of 1898 declared that the tactical unit "now be called the brigade-division, and that all other matters should give way to the full development of the Lieutenant Colonels command". So the concept of a tactical unit of a number of Batteries was established.

Why call it a Brigade ? Would this not be confused with an infantry brigade ? Why not call it a battalion ? In 1771 battalions had been formed ?

The Long Long Trail details what Brigades of the Royal Field Artillery consisted of and the key changes during WW1:

What was an artillery brigade?

Artillery Brigades Order of Battle:

• Aug 1914 - Gun Brigades consorted of three batteries. Howitzer Brigades consorted of two batteries
• May 1916 - Additional Howitzer Brigades formed and Howitzer Brigades broken up to form mixed Gun/Howitzer Brigades. Brigade Ammunition Columns disestablished.
• Jan 1917 - Some Brigades broken up tp provide additional guns to batteries

Brigades consisted of two or three sections, the section having two guns of sub sections.