For approximately two centuries, a great number of able-bodied young Irishmen emigrated from Ireland. This migration, which took place over the 17th and 18th centuries, is colloquially known as the 'Flight of the Wild Geese'.
The exodus began at the end of the Elizabethan wars, which were a series of revolts that began in 1569, and with the defeat of the Irish rebels at Kinsale in 1602. The bitter loss was followed by the Flight of the Earls in 1607, in which the outlawed rebel leaders, Hugh O'Neill, the Earl of Tyrone, and Hugh Roe O'Donnell, the Earl of Tyrconnell, fled to France with 99 other influential Irishmen of Ulster. The possessions of the insurgents were forfeited to the Crown. Furthermore, the six Ulster counties of Armagh, Tyrone, Derry, Donegal, Fermanagh, and Cavan were confiscated. The Crown established the Plantation of Ulster, in which the ancestral homelands of the Irish were distributed among English and Scottish Protestant settlers. The dispossessed Irish were deported to Connaught and Munster.
Many Irish, especially those who had fought in the rebellion, also chose to flee to continental Europe. France was one of the most favored destinations for the Irish, because it was overwhelmingly Roman Catholic. Once there, they frequently entered military service. Throughout the 17th and 18th centuries, the Catholic French were sympathetic to the Irish cause and they often smuggled luxury commodities to the Emerald Isle, in exchange for high-quality Irish wool and Irish military recruits. The recruits, who were equally prized, were customarily referred to in the ships' cargo logs as wild geese in order to mask the illicit recruitment; the name stuck and the military exiles came to be popularly known as 'Wild Geese'.
In the foreign military services, the recruits formed the 'Irish Brigades' and Irish soldiers were justly famed for their courage and fighting skill. Although the Irish Brigades were most prominent in the service of France, they were also active in the Austrian, Italian, and Spanish armies. Many Irish soldiers gained commissions as officers in token of the high regard in which they were held.
In the ensuing decades, the Wild Geese continued to flood into continental Europe from Ireland. This was particularly true during the Cromwellian Transplantation of the 1640's, when great numbers of Irish landowners had their estates confiscated and were transplanted or exiled. At this time, numerous Irish septs migrated to France in their entirety. After the broken terms of the Treaty of Limerick and the inaction of the harsh, anti-Catholic Penal Laws following the Irish resistance to William of Orange's 'Glorious Revolution', many Jacobites migrated to France from Ireland. In fact, the entire Jacobite army fled to France, and the former British King James II reviewed an army of 21,000 soldiers at Vannes in 1692.
The Irish Brigades were active throughout the next century. They were involved in an abortive French invasion of Britain in 1759, and it was hoped that the Catholic population of Ireland would rise up to support the invasion force. However, the glorious return of the 'Wild Geese' was prevented by the defeat of the French fleet at sea.
In the two centuries between the 'Flight of the Earls' and the French Revolution, hundreds of thousand of Irish migrated to continental Europe. In fact, it has been estimated that during the time of the Jacobite uprisings between 1691 and 1745, over 450,000 Irishmen died in the service of France alone. As such, the 'Flight of the Wild Geese' represents one of the most massive migrations in the history of Ireland.