War of Independence: how the IRA was structured

An IRA company was usually organised at the townland level, and could contain between 60 and 200 men

The IRA during the War of Independence sought to organise itself on the lines of a regular army though it operated as a guerrilla force.

It adopted the British army command structure of companies, battalions, brigades, divisions and then at the top was general headquarters.

A company was usually organised at the parish/townland level, and could contain between 60 and 200 men. Companies from the same town were identified by a letter rather than a number - hence D Company, Ferbane.

Battalions were organised in contiguous geographical areas, and usually comprised four or five companies. They were often grouped together in relation to electoral districts.


These in turn were grouped into brigades depending on the size of the county. Cork had four brigades, Kerry three, Offaly two and smaller counties like Longford and Carlow had one each.

Brigades did not always adhere to county boundaries. For instance the Mayo East Brigade also operated in Sligo and Roscommon, Sligo 1 Brigade in north Leitrim, the Offaly 2 Brigade in Westmeath and Dublin I Brigade included the whole of Wicklow.

The imposition of divisions on the brigade structure of the IRA was a relatively late inclusion in the War of Independence, and these were intended to become active if the truce broke down and hostiles recommenced.

The nominal rolls of the IRA which were released in 2014 list 115,000 men who served in the organisation during the War of Independence, but many historians believe this figure is an exaggeration, with many so-called “trucilliers” signing up after hostilities ended.