The Defenders originated in County Armagh in Ulster in 1784, to protect Catholics from attack by the Protestant "Peep O'Day Boys". Sectarian conflict had arisen out of the entry of Catholics into the linen producing business and their being blamed for the downturn in the market, although the actual cause was the increasing industrialisation of the business which was steadily eroding the previous largely cottage-based nature of the industry. Violence continued until the Battle of the Diamond in 1795 saw the "Peep O'Day Boys" emerge victorious. This victory was marked by the foundation of the Orange Order and the waging of a campaign of ethnic cleansing in mid Ulster which forced thousands of Catholics to seek refuge in Connaught and Leinster, and in many cases, bringing the Defender organisation with them.

The Defenders were usually depicted as subject to residual sectarianism, ultra-Catholic, guilty of anti-Protestantism and having only paid at best lip service to the non-sectarian ideals of the United Irishmen. While this was undoubtedly true of a proportion of Defenders, Catholic priests were not immune to their wrath as in Athlone in 1793 where a priest who preached in favour of the Militia Act was almost hanged to death.

The fortunes of the Defenders were closely tied to the United Irishmen by the outbreak of the rebellion in 1798 and they did not survive its failure; however their influence endured in the later formation of similar groups like the Ribbonmen in the 1830s.

From "Defenders (Ireland)" at www.wikipedia.org