George Nisbet was born in Rouen of a Glasgow father who in 1848 emigrated to Egypt, where he died. His widow married a Turk named Osman, who adopted her son and made him heir to his slave business. George Nisbet took the name of Osman Ali, and after being educated at the military academy, where he was intimate friend of the late Arabi Pasha, became a slave trader. 
A writer in the St Jame’s Gazette discussing various stories as to the origin of Osman Digna says-
About a year ago one who professed to possess undoubted sources of information on the subject gave me, with assurance of this remarkable man. He is not a Soudanese and not a Turk, but a Scotchman, and his name is George Nisbet. His father was an adventurous Glasgow man who in the thirties found himself a merchant in Rouen. Here his son George was born in 1836, and here the first 10 or 12 years of the boy’s life was spent. March revolutions and short lived republics were not, however mush to taste of the older Nisbet, and hearing of great things that were being done by Mehemet Ali in Eygpt, and of good opening for trade at Alexandria, he migrated to that city in 1848, only to fall victim to fever a few months after starting in business. His wife then married a Turkish trader named Osman, a man of some means and position, who adopted young Nisbet, made a Mussulman of him, named him Osman Ali and sent him in the military school at Cairo. Here Osman met and became attached to young fellow cadet, Achmet Arabi of whom Europe heard much later on as Arabi the Eygyptian or Arabi Pasha. Meanwhile Osman the Turk had settled in Suakim, had married the Hadenddawa Sheik’s daughter, and amassed great wealth as a slave dealer. On his death George Nisbet, or Osman Ali, gave up his military career, and as sole heir took over his adoptive father’s business as a slave dealer. Now began his grievances against the civilization which he had abandoned. Under English and French pressure the Egyptian Government was making efforts to repress the slave trade, and this tended to the ruin of Osman’s business. Then came the movement of his old friend Arabi against the dual control, and finally the rising of the Mahdi, in which he has done his best to wipe out old scored against England and against Egypt. - 
Osman Digma a Scot. Osman Digma, who for years has been giving the British trouble on the Upper Nile is according to the Pall Mall gazette, really a Scotchman name George Nisbet. He was born in Rouen of a Glasgow father who in 1848 emigrated to Egypt, where he died. His widow married a Turk named Osman, who adopted her son and made him heir to his slave business. George Nisbet took the name of Osman Ali, and after being educated at the military academy, where he was intimate friend of the late Arabi Pasha, became a slave trader. The harm done to his business by the English and French interference in Egypt, and the fall of Arabi Pasha, turned him against his former countrymen. He must be over 60 years of age now. 
And another article Among the most interesting episodes of Field Marshall Lord Kitchener’s sojourn in Eygpt and in the Soudan this winter was his interview at Wadi Halfa with his old enemy, Osman Digna. Time and again Osman Digna had defeated mingled Anglo-Egyptian forces. He cost the English army many a gallant officer. It was he upon whom the Kalifa relied to check Kitchener’s final advance upon Khartoum. He was defeated after particular heavy fighting at the battle of Athara, and again after the battle of Omdurman. Most people imagined that he had fallen in that battle, in which more than 10,000 dervishes lost their lives and 4000 were captured, or else that he had been slain when in the following year Kitchener’s successor as sirdar, General Sir Francis Wingate, overtook the remaining dervish forces at Abu Adil, on the White Nile, where, after a hard fought battle, the Khalifa and his principal emirs submitted to death rather than to capture,. At any rate, from that time forth Osman Digna disappeared from public print. Few ever learned that nearly 12 months later he was quietly captured by Captain Burgess near Tokar, where he had so signally defeated General Valentine Baker Pasha just 16 years previously, and conveyed first to Suez, and then via Cairo up to the Nile. He has ever since been detained in captivity at Wadi-Halfi as a prisoner of state. Indeed, it was only Lord Kitchener’s visit to his old time foe, when passing through Wadi.Halfa, that had really called to popular attention the fact that Osman Sigma is still in the land of the living.
What renders Osman Digma an object of such particular interest is the fact that this old veteran dervish is an Oriental only by adoption, and a Moslem by conversion, being a native of France, where he was born on the banks of the Seine in 1836, as the son of a certain Joseph Nisbet and his wife, Marie. The boy was duly christened in the cathedral at Rouen, receiving the name of Georges. When he was about 11 years old his father failed in business, and thereupon migrated with his wife and son to Egypt, where he died some months later at Alexandria. His widow, who found herself almost penniless, contracted a few months later a marriage, according to Moslem rites, with a well known Mahometan merchant of Alexandria, Osman Digna by name. Having no children of his own, he became extremely fond of young Georges Nisbet, insisting on his becoming a convert to Islam, and entered him under the name of Osman Digna, the younger, at the military college at Cairo, where the lad received a careful training at the hands of the distinguished French and British officers attached to the college as professors.
HIS RISE TO POWER In 1860 the whole family took up their residence at Suakim, where Osman Digma the elder soon became knowm as the leading merchant, and incidentally, too, as the principal slave dealer of the entire Red Sea littoral. On his death in 1865, his stepson, the former Georges Nisbet, inherited his fortune and his business, and, under the name of Osman Digna, soon acquired even greater wealth, power, and influence. When the insurrection broke out in Cairo in 1882, he warmly espoused the cause of Arabi Pascha, the rebel leaser, who was and old classmate and friend of his. It was on this occasion that he was elected chief by the Sheiks of the Eastern Soudan. So great was his power that both the Mahdi and his successor Khalifa were forced to treat “ the French Arab” as he used to be styled, with extreme consideration, and to defer his wishes.
Osman Digna decided to throw in his lot with Madhi after the suppression of the Arabi rebellion by Lord Wosleley. It was because the English, by their efforts to stamp out the slave trade, had virtually ruined the extremely lucrative part of his business. Osman Digna in those days was a man of herculean stature, which is now probably bent by his 81 years. His eyes were of piercing blackness, looking forth from beneath shaggy eyebrows, and he wore an immense beard. He lost his left arm in one of the battles around Tokar in the early stages of the dervish insurrection, and it was his exceptional stature and the absence of his left arm that caused him to be recognized by Captain Burgess, in 1900, when he was endeavouring to escape across the Red Sea into the fastnesses of Arabia. KITCHENER AND OSMAN DIGNA. 
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