The Flight of the Wild Geese refers to the departure of an Irish Jacobite army under the command of Patrick Sarsfield from Ireland to France, as agreed in the Treaty of Limerick on October 3, 1691, following the end of the Williamite War in Ireland. More broadly, the term "Wild Geese" is used in Irish history to refer to Irish soldiers who left to serve in continental European armies in the 16th, 17th and 18th centuries, or even, poetically, Irish soldiers in British armies as late as the First World War.

Spanish service:
The first Irish troops to serve as a unit for a continental power formed an Irish regiment in the Spanish Army of Flanders in the Eighty Years' War in the 1580s. The regiment had been raised by an English Catholic, William Stanley, in Ireland from native Irish soldiers and mercenaries, whom the English authorities wanted out of the country. (See also Tudor re-conquest of Ireland) Stanley was given a commission by Elizabeth I and was intended to lead his regiment on the English side, in support of the Dutch United Provinces. However, in 1585, motivated by religious factors and bribes offered by the Spaniards, Stanley defected to the Spanish side with the regiment. In 1598 Diego Brochero de Anaya wrote the Spanish King Philip III:

"that every year Your Highness should order to recruit in Ireland some Irish soldiers, who are people tough and strong, and nor the cold weather or bad food could kill them easily as they would with the Spanish, as in their island, which is much colder than this one, they are almost naked, they sleep on the floor and eat oats bread, meat and water, without drinking any wine."

The unit fought in the Netherlands until 1600 when it was disbanded due to heavy wastage through combat and sickness.

Following the defeat of the Gaelic armies of the Nine Years' War, the "Flight of the Earls" took place in 1607. The Earl of Tyrone Hugh O'Neill, the Earl of Tyrconnell Rory O'Donnell and the Lord of Beare and Bantry, Donal O'Sullivan, along with many chiefs and their followers from Ulster, fled Ireland. They hoped to get Spanish help in order to restart their rebellion in Ireland, but King Philip III of Spain did not want a resumption of war with England and refused their request.

Nevertheless, their arrival led to the formation of a new Irish regiment in Flanders, officered by Gaelic Irish nobles and recruited from their followers and dependents in Ireland. This regiment was more overtly political than its predecessor in Spanish service and was militantly hostile to the English Protestant government in Ireland. The regiment was led by Hugh O'Neill's son John. Prominent officers included Owen Roe O'Neill and Hugh Dubh O'Neill.

A fresh source of recruits came in the early seventeenth century, when Roman Catholics were banned from military and political office in Ireland. As a result, the Irish units in the Spanish service began attracting Catholic Old English officers such as Thomas Preston and Garret Barry. These men had more pro-English views than their Gaelic counterparts and considerable animosity was created over plans to use the Irish regiment to invade Ireland in 1627. The regiment was garrisoned in Brussels during the truce in the Eighty Years' War from 1609-1621 and developed close links with Irish Catholic clergy based in the seminary there, creating the famous Irish Colleges - most notably, Florence Conroy.

Many of the Irish troops in Spanish service returned to Ireland after the Irish Rebellion of 1641 and fought in the armies of Confederate Ireland - a movement of Irish Catholics. When the Confederates were defeated and Ireland occupied after the Cromwellian conquest of Ireland, around 34,000 Irish Confederate troops fled the country to seek service in Spain. Some of them later deserted or defected to French service, where the conditions were deemed better. At the time of the Napoleonic Wars there were still three Irish infantry regiments in the Spanish army: Irlanda (raised 1698); Hibernia (1709); and Ultonia (1709). However in the later years of the existence of these units only the officers were Irish or of Irish descent, the men being predominantly Spanish or other foreigners. All three regiments were finally disbanded in 1815.

French service:

From the mid-17th century or so, France overtook Spain as the destination for Catholic Irishmen seeking a military career. The principal reason for this was that France was an ascendant power, rapidly expanding its armed forces, whereas Spain was a power in decline.

France recruited many foreign soldiers; Germans, Italians, Walloons and Swiss. André Corvisier, the authority on French military archives, estimates that foreigners accounted for around 12% of all French troops in peacetime and 20% of troops during warfare. In common with the other foreign troops the Irish regiments were paid more than their French counterparts. Both Irish and Swiss regiments in French service wore red uniforms, though this had no connection with the redcoats of the British army.

The crucial turning point came during the Williamite War in Ireland (1688-91), when Louis XIV gave military and financial aid to the Irish Jacobites. In return for 6000 French troops, Louis demanded 6000 Irish recruits for use in the Nine Years War against the Dutch. These men, led by Justin McCarthy, Viscount Mountcashel formed the nucleus of the French Irish Brigade.

Later, when the Irish Jacobites under Patrick Sarsfield surrendered at the Treaty of Limerick, they were allowed to leave Ireland for service in the French Army. Sarsfield's "exodus" included 14,000 soldiers and 10,000 women and children. This is popularly known in Ireland as the "Flight of the Wild Geese".

Initially, these units were not integrated into the French Army, but were assigned to the court in exile of James II, deposed in the Glorious Revolution, whom Louis deemed the legitimate King of England, Ireland and Scotland. They were later incorporated into the Irish Brigade of the French Army.

Like the earlier Irish units in Spanish service, the French Irish regiments were quite politicised, being composed of dispossessed Irish Catholics, who were committed to a Stuart restoration in Britain and Ireland. Famously, the Irish Brigade distinguished themselves in the Battle of Fontenoy against British troops in 1745.

Up until 1745, Catholic Irish gentry were allowed to recruit soldiers for France in Ireland. The authorities in Ireland saw this as preferable to the potentially disruptive effects of having large numbers of unemployed young Catholic men of military age in the country. However, after a composite Irish detachment from the French Army (drawn from each of the regiments comprising the Irish Brigade and designated as "Irish Picquets") was used to support the Jacobite Rising of 1745 in Scotland, the British realised the dangers of this policy and banned recruitment for foreign armies in Ireland. After this point, the rank and file of the Irish units in French service were increasingly non-Irish although the officers continued to be recruited from Ireland.

During the Seven Years' War efforts were made to find recruits from amongst Irish prisoners of war or deserters from the British Army. Otherwise, recruitment was limited to a trickle of Irish volunteers who were able to make their own way to France, or from the sons of former members of the Irish Brigade who had remained in France. During the Seven Years War the Irish Regiments in French service were: Bulkeley, Clare, Dillon, Rooth, Berwich and Lally. Additionally, there was a regiment of cavalry, Fitz James. By the end of the 18th century even the officers of the Irish Regiments were drawn from Franco-Irish families who had settled in France for several generations. While often French in all but name, such families proudly retained their Irish heritages.

Following the outbreak of the French Revolution the Irish Brigade ceased to exist as a separate entity on 21 July 1791 when the 12 non-Swiss foreign regiments then in existence were integrated into the line infantry of the French Army, losing their distinctive status, titles and uniforms. Many left the service in 1792 when Louis XVI was deposed, as their oath of loyalty was to him and not to the French people. Napoleon Bonaparte subsequently raised a small Irish unit composed of veterans of the Irish Rebellion of 1798.

Austrian service:

Throughout this period, there were also substantial numbers of Irish officers and men in the armies of the Austrian Habsburg Empire, many of whom were based in Prague. The most famous of these was Peter Lacy, a Field Marshal in the Imperial Russian Army, whose son Franz Moritz Graf von Lacy excelled in the Austrian service. General Maximilian Ulysses Graf von Browne, the Austrian commanding officer in the Battle of Lobositz, was also of Irish descent. Recruitment for Austrian service was especially associated with the midlands of Ireland and with the Taaffe O'Neillan and O'Rourke gentry families. Much earlier, in 1634, during the Thirty Years' War, Irish officers led by Walter Deveraux assassinated general Albrecht von Wallenstein on the orders of the Emperor. In the 19th century, further Irish officers served in the Habsburg Empire, so Laval Graf Nugent von Westmeath and Maximilian Graf O'Donnell von Tyrconnell, who saved the life of Emperor Franz Joseph I during an assassination attempt. Gottfried von Banfield finally became the most successful Austro-Hungarian naval aeroplane pilot in the First World War.

Swedish service:

In 1609, Arthur Chichester, then Lord Deputy of Ireland, deported 1300 former rebel Irish soldiers from Ulster to serve in the Protestant Swedish Army. However, under the influence of Catholic clergy, many of them deserted to Polish service.

Polish service:

The Catholic Irish troops in Protestant Swedish service changed sides during a battle against largely Catholic Poland, the only European country with statutory freedom of religion at the time. The Irish then served in Polish service for several years during the Polish-Muscovite War (1605-1618), until their wages went unpaid.

Italian service:

Despite being less studied, the ancient and traditional "mestiere delle armi" in Italy was also a well-known profession by the Irish. The "tercio" of Lucas Taf (around 500 men) served in Milan towards 1655. The Army of Saboya included also Irishmen, but in Italy the Irish were organized basically by the Spanish administration. In 1694 another regiment in Milan was exclusively composed by Irishmen. Around the 3-4% of a total of 20.000 men were Irish in the Spanish Army of Milan. It is not a high figure, but it was important as regards quality. In this context, James Francis Fitz-James Stuart (1696-1739), Duke of Berwick and of Liria is just one example of this success. He began to serve the Monarchy in 1711 and succeeded in becoming General Lieutenant (1732), ambassador in Russia, in Austria and in Naples, where he died. In 1702 an Irish grenadier company led by Francis Terry entered Venetian service. This company of Jacobite exiles served at Zara until 1706. Colonel Terry became the Colonel of a Venetian Dragoon Regiment, which the Terry family mostly commanded until 1797. Colonel Terry's Dragoons uniforms were red faced blue in the Irish tradition. The Limerick Regiment, of Irish Jacobites, transferred from Spanish service to that of the Bourbon king of Sicily in 1718.

End of the Wild Geese:

Irish recruitment for continental armies dried up after it was made illegal in 1745. In 1732 Sir Charles Wogan indicated in a letter to Dean Swift that 120,000 Irishmen had been killed and wounded in foreign service "within these forty years", with Swift later replying:

"I cannot but highly esteem those gentlemen of Ireland who, with all the disadvantages of being exiles and strangers, have been able to distinguish themselves by their valour and conduct in so many parts of Europe, I think, above all other nations."t was some time before the British armed forces began to tap into Irish Catholic manpower. In the late eighteenth century, the Penal Laws were gradually relaxed and in the 1790s the laws prohibiting Catholics bearing arms were abolished.

Thereafter, the British began recruiting Irish regiments for the Crown Forces - including such famous units as the Connaught Rangers. Several more Irish units were created in the 19th century. By 1914 specifically Irish infantry regiments in the British Army comprised the Prince of Wales's Leinster Regiment, the Royal Dublin Fusiliers, the Irish Guards, the Royal Irish Regiment, the Royal Inniskilling Fusiliers, the Royal Irish Rifles, the Royal Irish Fusiliers, the Connaught Rangers and the Royal Munster Fusiliers. With the creation of the Irish Free State in 1922 five of the above regiments were disbanded, with most of the remainder undergoing a series of amalgamations between 1968 and 2006. The United Kingdom still retains three Irish regiments: the Irish Guards, the Royal Irish Regiment, and the London Irish Rifles.