The three "Irish" regiments, like other units before them, such as the
Irish Tercio (
Tercio de irlandeses), also known as the Irish Brigade, which was raised in 1605 by
Henry O'Neill to be incorporated into Spain's
Army of Flanders, were raised from among the thousands of young Irishmen who, due to the
Penal Laws, left their homes to take service with France and Spain. The
Hibernia Regiment was raised in 1703 (or 1709) by order of
Philip V, from troops and officers from Spain's forces in France and Ultonia was raised later that same year. Although the service records give no reasons for the transfers, there was a certain amount of mobility among the three sister regiments, which may have been due to the need to raise the number of men under arms before a specific military action. One notable case is that of
Alejandro O'Reilly (1723–1794), who enlisted in the
Hibernia Regiment in 1735 and worked his way up to lieutenant general (1767) before transferring to the Irlanda Regiment in 1772. The 90 service records collected in the
Libro de oficiales, sargentos primeros y cadetes del regimiento Irlanda (
Register of Officers, Sergeants and Cadets of the Irlanda Regiment), drawn up by Lieutenant Colonel Juan MacKenna while the regiment was stationed at
Tortosa in December 1774, shows that of the 21 staff officers and captains, all of whom were Irish-born, twelve had served exclusively with the Irlanda, while the remaining nine had previously served with other regiments. Among the 19 lieutenants and aides-de-camp, all of whom were also Irish-born, all had served exclusively with the Irlanda, except for one, who had transferred from the Hibernia. Among the 18 sub-lieutenants, none of whom had seen active service, eleven had served exclusively in the Irlanda while five had been transferred from the Ultonia Regiment at around the same time (1771–1721), one had been transferred from the Hibernia Regiment and another from the Asturias Regiment, all during that same period. As for the seventeen sergeants, none of whom were Irish, being mainly French (8) and Italian (7). All were experienced soldiers; three of the Italians and two of the Frenchmen had served exclusively with the Irlanda. Of the fifteen cadets, all Irish, none of whom had seen active service, three had been transferred from the Hibernia Regiment in 1774. On the other hand,
Joseph O'Donnell y O'Donnell, who enlisted in the Irlanda Regiment in 1739 and became its colonel in 1777, enlisted his three eldest sons, Leopoldo,
Joseph (José) and
Charles (Carlos), as boy cadets in the Irlanda and his three youngest sons,
Henry (Enrique), Alejandro and Francisco, in one of the other sister regiments, the
Hibernia Regiment. All six saw action during the
Peninsular War ==History==