Walter Devereux , 1st Earl of Essex Walter Devereux , 1st Earl of Essex , KG ( 16 September 1541 – 22 September 1576 ) , an English nobleman and general . From 1573 until his death he fought in Ireland in connection with the Plantation of Ulster , where he ordered the massacre of Rathlin Island . He was the father of Elizabeth I ' s favourite of her later years , Robert Devereux , 2nd Earl of Essex . Family . Walter Devereux was the eldest son of Sir Richard Devereux , who was admitted to the Order of the Garter on 20 February 1548 and died in the same year , in the lifetime of his father , Walter Devereux , 1st Viscount Hereford . Walter Devereux ' s mother was Dorothy Hastings , daughter of George Hastings , 1st Earl of Huntingdon and Anne Stafford , said to have been a mistress of Henry VIII . Through both his parents he was related to the Bourchier family , to which previous Earls of Essex had belonged : John Devereux , son of Walter Devereux who died at the Battle of Bosworth , married Cecily Bourchier , sister of Henry Bourchier , Earl of Essex . Career . In 1558 , Devereux ' s grandfather died and he became 2nd Viscount Hereford and 10th Baron Ferrers of Chartley . He provided signal service in suppressing the Northern Rebellion of 1569 , serving as high marshal of the field under the Ambrose Dudley , 3rd Earl of Warwick and Lord Clinton . For his zeal in the service of Queen Elizabeth I on this and other occasions , he was made a knight of the Garter and was created Earl of Essex in 1572 . Eager to give proof of " his good devotion to employ himself in the service of her Majesty , " he offered on certain conditions to subdue or colonise , at his own expense , a portion of the Irish province of Ulster . At that time , Ulster was completely under the dominion of the O ' Neills , led by Sir Brian MacPhelim and Turlough Luineach , and of the Scots led by Sorley Boy MacDonnell . His offer , with certain modifications , was accepted . He set sail for Ireland in July 1573 , accompanied by a number of earls , knights and gentlemen , and with a force of about 1200 men . His enterprise had an inauspicious beginning ; a storm dispersed his fleet and drove some of his vessels as far as Cork and the Isle of Man . His forces did not all reach the place of rendezvous till late in the autumn , and he was compelled to entrench himself at Belfast for the winter . Here his troops were diminished by sickness , famine and desertion to not much more than 200 men . Intrigues of various sorts and fighting of a guerilla type followed , and Essex had difficulties both with his deputy Fitzwilliam and with the Queen . He was in dire straits , and his offensive movements in Ulster took the form of raids and brutal massacres among the O ' Neills . In October 1574 , he treacherously captured MacPhelim at a conference in Belfast , and after slaughtering his attendants , had MacPhelim , his wife and brother executed at Dublin . He arrested William Piers , who had been active in driving the Scots out of Ulster , and accused him of passing military intelligence to Brian mac Phelim O ' Neill . Essex ordered Piers ' s arrest and detention in Carrickfergus Castle in December 1574 , but Piers was freed and he successfully executed Brian mac Phelim O ' Neill for treason . After encouraging Essex to prepare to attack the Irish chief Tirlogh Luineach , apparently at the instigation of the earl of Leicester , the queen suddenly commanded him to " break off his enterprise . " However , she left him a certain discretionary power , and he took advantage of that to defeat Turlogh Luineach and chastise County Antrim . He also massacred several hundreds of Sorley Boy ' s following , chiefly women and children , who had hidden in the caves of Rathlin Island in the face of an amphibious assault led by Sir Francis Drake and Sir John Norreys . He returned to England at the end of 1575 , resolved " to live henceforth an untroubled life . " He was however persuaded to accept the offer of the queen to make him Earl Marshal of Ireland . He arrived in Dublin in September 1576 , but died three weeks later of dysentery . It was suspected that he had been poisoned at the behest of the Earl of Leicester , who married his widow two years later . A post - mortem was carried out and concluded that Essex had died of natural causes . He was succeeded in the Earldom of Essex by his son Robert . Marriage and issue . In 1561 or 1562 , Devereux married Lettice , daughter of Sir Francis Knollys and Catherine Carey . Walter and Lettice had two sons , Robert and Walter , as well as two daughters , Penelope and Dorothy . Another son , Francis , died as an infant . Penelope married Robert Rich , 3rd Baron Rich and her sister Dorothy married Henry Percy , 9th Earl of Northumberland