O'Byrne, Aodh (c.1520–1579), lord of Crioch Raghnuill, was the eldest son of Seán O'Byrne (qv), lord of Crioch Raghnuill, and his wife, Doireann O'Byrne. After the collapse of the Kildare hegemony in 1535, Toirdhealbhach O'Toole (qv), lord of Fartry and Fercullen, and the O'Byrnes allied with the young Domhnall MacMurrough Kavanagh (qv) of Garryhill – described surprisingly as king of Leinster in the short Annals of Leinster – and the Art Boy Kavanaghs of the Blackstairs mountains to advance their power in east Leinster. This strong alliance provoked major government campaigns against them in May 1539 and June 1540; in November 1540 Sir Anthony St Leger (qv) and James Butler (qv), 9th earl of Ormond, forced them to submit, and Toirdhealbhach was dispatched to England before April 1541 to make his submission to Henry VIII. On 4 July that year Tadhg mac Gerald O'Byrne of Kiltimon and his leading nobles, including Seán, agreed to the gradual introduction of English rule into their lordship as part of the policy of surrender and regrant; while the agreement ostensibly allowed the O'Byrnes considerable autonomy over their own affairs, in fact it paved the way for the replacement of the O'Byrne lordship by an English seneschalsy.
Peace proved brief. Early in 1542 Toirdhealbhach O'Toole was killed by his rival Toirdhealbhach mac Seaain O'Toole of Imaal (d. 1547) in a surprise morning attack upon his camp. His death opened the way to power for Seán and Aodh, who became leaders of the Irish in the Leinster mountains, and led them into direct conflict with the Butlers of Ormond, who sought to extend their authority into the Wicklow district known as Cosha (north-east of Shillelagh), a territory where all the senior O'Byrne branches held lands. The O'Byrnes of Glenmalure had also moved into Cosha, and seized a large slice of this territory centred on the parishes of Kilcommon and Preban near to Aughrim and Tinahely, posing a major obstacle to the Butler advance. In October 1543 the Butlers appointed Sir John Travers (d. 1561), a Palesman, constable of Arklow, with instructions to enforce their old claims to these lands. Although Travers failed in this objective, his attacks upon the O'Byrnes of Glenmalure and forays against the O'Tooles and the MacMurrough Kavanaghs seriously disturbed the Irish and fuelled the ambitions of the O'Byrnes of Glenmalure, who, having withstood the Butler assault, now saw themselves as the emerging regional power.
About this time Aodh took as his first wife Sadhbh, daughter of Feilim Buidhe O'Byrne of Clonmore, with whom he had two children – his eventual heir Fiach O'Byrne (qv) (d. 1597) and a daughter, Elizabeth, who were born at Ballinacor in Glenmalure about 1544. Although Aodh commissioned poems in honour of his wife, their marriage did not last: about 1549 they divorced and before August 1550 Aodh married Sadhbh, daughter of Art Óg O'Toole of Castlekevin (d. 1546).
In 1545 the ambitions of Aodh and his father received a serious check when Cathaoir MacMurrough Kavanagh (qv) defeated them and their kinsman Gerald MacMurrough Kavanagh (qv) of Garryhill in a pitched battle near Hacketstown. They retreated to the safety of the forests and hills of their lordship to rethink their strategy and re-emerged from Glenmalure to begin a lucrative business in the levy of blackrents upon English and Irish settlements. Their rise coincided on the one hand with the recall of St Leger to England in spring 1546 to answer charges against him, and on the other with a series of attacks made by Brian O'Connor Faly (qv) and Giollapadraig O'More (d. 1549) in late 1546 on the settlers in the midlands. Before his departure St Leger appointed Lord Justice Sir William Brabazon (qv) to govern Ireland, mistakenly advising him that the O'Byrnes and the O'Tooles were a spent force.
The rise of Aodh had its origins in the violent imposition of the plantations, which profoundly disturbed the Irish of Leinster and the midlands and irrevocably redefined Irish politics, causing a decisive eastward shift of the provincial centre of gravity to the Wicklow mountains. From there Aodh and his father offered refuge to the dispossessed in their virtually impenetrable territory of Glenmalure, enhancing both their military manpower and their social status through their patronage of poets. The death of Art Óg O'Toole before November 1546 left them as the only leaders of the mountain lords, and they proved their strength by defying Brabazon's expedition against them between 1 April and December 1546. After the collapse of the O'Tooles of Imaal and the Fitzgerald rebels in summer 1547, their influence extended into west Wicklow and east Kildare, while to the south, they consolidated their hold upon their threatened lands of Kilpipe and Preban. In July 1548 the Butlers moved to halt the development of the O'Byrne hegemony over the Wicklow mountains, launching an attack by Tibbot Walsh, constable of Arklow, and the O'Byrnes of Newrath, which forced Seán and Aodh to retreat high into the Wicklow uplands. Facing defeat, Seán dispatched a letter begging protection from Sir Edward Bellingham (qv), who had been dispatched by the English council to restore order in Ireland. Bellingham intervened with the Butlers, depriving them of their victory. Aodh and his father benefited from this breathing space, and in September 1548 began a fresh assault on the Pale. They changed their tactics, playing a double game with the English: while the son remained aloof, the father concluded a peace at Dublin during October 1548. Increasingly, though, Seán played a minor role in the affairs of Crioch Raghnuill, leaving them to the wily Aodh; he is last mentioned with his wife, Una, when he was pardoned in 1550, and he died the following year.
Aodh was now determined to become the leader of Gaelic Leinster and he consolidated his family's status, already advanced through marriage and patronage, by military support for the O'Connor Falys and O'Mores in Laois and Offaly during the 1550s and 1560s, and groomed his son Fiach to succeed him in that role; under the tutelage of his charismatic father, Fiach emerged as a hard-line but pragmatic warlord. As the 1560s wore on, Aodh's attacks became more ambitious and predatory, perhaps indicating Fiach's influence. In January 1563 the two received pardons, probably for their involvement in Richard Keating's disturbances in Wexford during summer 1562, and they were pardoned again in December 1563 for the kidnap of George Harvey and Henry Davells and an attack with the O'Tooles upon certain Talbots. Further attacks and raids in 1564–5 began to cause the government disquiet; when called to account in February 1566 Aodh promised to surrender Fiach, but failed to fulfil his pledge. Further pardons were granted in May 1567 and April 1569. Sir Francis Agard, seneschal of Crioch Branach and Crioch Raghnuill from 1566, recognised the danger that Fiach posed, but was dissuaded from taking any punitive action by his friendship with Aodh, who only encouraged his son to ever more daring sallies.
In 1569 the lord deputy Henry Sidney (qv) granted the Kavanagh lordship of Idrone to Sir Peter Carew (qv) the elder, provoking a revolt by the Kavanaghs and Sir Edmund Butler (qv), brother of Thomas Butler (qv), 10th earl of Ormond. Sir Edmund submitted to Ormond in September 1569, and was imprisoned in Dublin castle, but in November he escaped to Glenmalure with the help of Aodh's sons. Butler repaid this help by having an affair with Fiach's wife, resulting in Sadhbh's divorce from Fiach and enmity between the two men.
As Aodh began to age he gradually released the reins of power to his heir, and in the 1570s Fiach established himself as the leader of the Leinster Irish. In 1571 he formed an alliance with Ruaidhrí Óg O'More (qv) of Laois to attack the Pale. The following year Fiach and his brother-in-law Brian MacMurrough Kavanagh (qv) were implicated in the murder on 21 April 1572 of Robert Browne of Mulcranan, Co. Wexford, and in July Agard's men killed Aodh's brother for his alleged part in the murder. In August Sir Nicholas White (qv), seneschal of Wexford and Browne's father-in-law, returned from England; he obtained the support of the queen to take action against Fiach and his confederates and within days of his return attacked Crioch Raghnuill. In response Fiach and Brian Kavanagh ravaged Wexford, and with Ruaidhrí wreaked mayhem throughout Leinster. In February 1573 Aodh, Brian, and Fiach were pardoned after withdrawing their support from the actual murderers, Matthew and Robert Furlong.
Throughout that year Aodh and Fiach maintained contact with Gerald fitz James Fitzgerald (qv), 15th earl of Desmond, who hoped that Ruaidhrí and the O'Byrnes would rise up in Leinster during 1574. In preparation for war Aodh recruited mercenaries and made two marriage alliances to strengthen his regional position: Fiach was married to Rose (qv), daughter of Fiach O'Toole (qv) of Castlekevin and Rose Basnett; and in November 1573 Ruadhrí married Margaret O'Byrne, Aodh's daughter. On his return from his sister's wedding, Fiach was ambushed by the sheriff of Kildare, Sir Piers Fitzgerald, but he ensnared Fitzgerald and escorted him to Glenmalure. Fiach and Aodh refused Agard's request for a parley to negotiate the sheriff's release and demanded a ransom of £800. As planned, the O'Byrnes revolted in March 1574, while Ruaidhrí raided the southern Pale. In early October Aodh opened negotiations with Ormond, though his intentions were devious: in an echo of his father's proceeding in 1548, he left Fiach in charge and gave himself into the custody of Ormond, arriving in Dublin on 24 October. In February 1575 Gerald Fitzgerald (qv), 11th earl of Kildare and governor of the Pale's south-western border, was arrested on suspicion of conspiring with the O'Byrnes and Ruaidhrí to force Elizabeth to make him lord deputy; among the allegations was that Kildare had held all-night conferences with the lords of Glenmalure and their O'More protégé at Kilkea castle between 1572 and 1575, and that Fiach had acted as the earl's henchman, attacking his enemies. It was even alleged that the earl tried, unsuccessfully, to persuade Aodh to have the captive sheriff murdered in 1573–4. Kildare was imprisoned in England, but nothing was proved and he returned to Ireland in 1577.
Aodh made the most of the earl's absence, authorising Ruaidhrí and Fiach to burn throughout Co. Kildare. During Lord Deputy Sidney's circuit through east Leinster in November and December 1575, Aodh freely met him without protection, but Fiach remained aloof. Ceaseless intimidation by Sir Francis Cosby (qv), seneschal of Laois (d. 1580), goaded Ruaidhrí to revolt in February 1577; murders such as that of the defenceless Muircheartach O'More, lord of Slemargy, Ruaidhrí's alleged ally, by Cosby and Robert Harpoole (d. 1594), sheriff of Carlow, profoundly shocked Gaelic Leinster. As a result fighting consumed the midlands and spread into Kildare and Carlow, where Naas and Leighlinbridge were burned by Ruaidhrí in May 1577. In the autumn Ruaidhrí captured Sir Henry Harrington (d. 1605) and Alexander Cosby (d. 1596), and during a rescue attempt by the planters in November, Aodh's daughter Margaret, Ruaidhrí's wife, was beheaded, two of their sons slaughtered, and Ruaidhrí himself seriously wounded. The killing of Aodh's son Seán within days of Margaret's death suggests that his father had ordered Fiach to intervene to support the beleaguered Ruaidhrí. After his recovery, Ruaidhrí with Aodh's approval led revenge attacks from Crioch Raghnuill upon Carlow and Kildare, which ended with his death in July 1578 in a skirmish with Brian MacGillapatrick (qv) of Upper Ossory.
As Fiach became more and more belligerent, Aodh outwardly became more friendly towards the government, concealing his anger behind a superficial charm and affability. In February 1579 he lavishly entertained Lord Justice Sir William Drury (qv) at Ballinacor; on this occasion he agreed to the inclusion of his lordship in the government's plans to shire the territories of Wicklow and Ferns. Aodh died some time in the summer of that year, his death extinguishing any moderating influence over Fiach and heralding increased conflict in Leinster.