Marie Edme Patrice Maurice de Mac-Mahon, duc de Magenta, Marshal of France (13 July 1808 - 16 October 1893) was a Frenchman of Irish descent. He served as Chief of State of France from 1873 to 1875 and as the first president of the Third Republic, from 1875 to 1879. To date, he and Charles de Gaulle (his maternal grandmother being a McCartan) are the only people of Irish descent to have served as heads of state in Continental Europe.

Military career
He served as Governor-General of Algeria from 1 September 1864, returning at the outbreak of the Franco-Prussian War, during which he led an Alsatian army unit (although attrition throughout the war led to men from other areas being added to this).
In the Franco-Prussian War MacMahon commanded the I and V French Corps on the Rhine Army's Southern line. On 4 August, 1870 the Prussian 3rd Army attacked the Southern line, and immediately won the border city of Wissembourg from the French; quickly moving onto capture the city of Woerth two days later.
After less than a week of fighting, the entire French Rhine Army's Southern line could not withstand the Prussian aggression and retreated West, further into French territory. The Prussians were relentless. The Prussian 3rd Army was capturing town after town, while their defeated opponents I and V Corps hastily retreated to Chalon-s.-Marne making sure to stay out of the way of the advancing Prussians by heading southwest while the Prussians drove West.
Mac-Mahon left his Corps and led the 120,000 strong remnants of the French Rhine army (I, VII, XII Corps) with Napoleon III. They began marching from Chalons-s.-Marne North/Northeast, in an attempt to rally the besieged army at Metz over 130 km to the East. But the Prussian 3rd Army advance was incredible; in less than 3 weeks the army covered over 325 km, and intercepted the French army along the Meuse River, and for three days battled it (29 to 31 August), forcing the French to fall to Sedan. Meanwhile, the Prussians had created a 4th Army, and marched the it to the southern flank of Sedan, while the 3rd Army dug in North of Sedan.
On 1 September 1870, the Prussians thus laid siege to the city of Sedan. Standing at the gates was a powerful force of 200,000 Prussian soldiers under the command of General Helmuth von Moltke. Mac-Mahon was highly indecisive, allowing the Germans to move in reinforcements to completely encircle Sedan.
Mac-Mahon was wounded and command passed to General De Wimpffen who announced the surrender of the French army. On 2 September Napoleon III surrendered, along with his remaining 83,000 French troops (Battle of Sedan).

Franco-Prussian War
When the Paris Commune was suppressed in May 1871, Mac-Mahon led the Versailles troops. The French army spent eight days massacring workers, shooting civilians on sight. Tens of thousands of Communards and workers were summarily executed (as many as 30,000); 38,000 others imprisoned and 7,000 were forcibly deported.
As president of France, he controversially dismissed the republican Prime Minister Jules Simon, replacing him with the Orleanist duc de Broglie, before dissolving the French National Assembly on 16 May 1877 in an effort to halt the rise of Republicanism and boost the prospects of a restoration of the monarchy under the Comte de Chambord. This event is known as the 16 May 1877 crisis.
The Assembly having (9 November 1873) fixed his term of office at seven years, he declared in a speech delivered 4 February 1874 that he would know how to make the legally established order of things respected for seven years. Preferring to remain above party, he rather assisted at than took part in the proceedings which, in January and February 1875, led up to the passage of the fundamental laws finally establishing the Republic as the legal government of France. And yet Mac-Mahon writes in his still unpublished memoirs: "By family tradition, and by the sentiments towards the royal house which were instilled in me by my early education, I could not be anything but a Legitimist." He felt some repugnance, too, in forming, in 1876 the Dufaure and the Jules Simon cabinets, in which the Republican element was represented.
When the episcopal charges of the bishops of Poitiers, Nimes, and Nevers, recommending the case of the captive Pope Pius IX to the sympathy of the French Government, were met by a resolution in the Chamber, proposed by the Left, that the Government be requested "to repress Ultramontane manifestations" (4 May 1877), Mac-Mahon, twelve days later, asked Jules Simon to resign, summoned to power a conservative ministry under the Duc de Broglie, persuaded the Senate to dissolve the Chamber, and travelled through the country to assure the success of the Conservatives in the elections, protesting at the same time that he did not wish to overturn the Republic. However, the elections of 14 October resulted in a majority of 120 for the Left; the de Broglie ministry resigned on 19 November, and the president formed a Left cabinet under Dufaure. He retained his office until 1878, so as to allow the Exposition Universelle to take place in political peace, and then, the senatorial elections of 5 January 1879, having brought another victory to the Left, Mac-Mahon found a pretext to resign (30 January 1879), and Jules Grévy succeeded him.
This soldier was not made for politics. "I have remained a soldier", he says in his memoirs, "and I can conscientiously say that I have not only served one government after another loyally, but, when they fell, have regretted all of them with the single exception of my own." In his voluntary retirement he carried with him the esteem of all parties: Jules Simon, who did not love him, and whom he did not love, afterwards called him "a great captain, a great citizen, and a righteous man" (un grand capitaine, un grand citoyen et un homme de bien). His presidency may be summed up in two words: on the one hand, he allowed the Republic to establish itself; on the other hand, so far as his lawful prerogatives permitted, he retarded the political advance of parties hostile to the Catholic church, convinced that the triumph of Radicalism would be to the detriment of France. The last fourteen years of his life were passed in retirement, quite removed from political interests.
He died at Montcresson, Loiret in 1893. He was buried, with national honours, in the crypt of the Invalides.

Quotes

Irish Brigade (French)
Flight of the Wild Geese
16 May 1877 crisis