Sadleir, George Forster (1789–1859), army officer and explorer, was born 19 January 1789 in Cork, third son of James Sadleir, cotton manufacturer and sheriff of Cork (1791), of Tipperary and later Shannon Vale House, Clonakilty, Co. Cork, and his wife Joanna, daughter of George Forster of Cork. His younger brother, Richard Sadleir, was a commander in the Royal Navy. The family was descended from John Sadleir of Stratford-upon-Avon, England, who came to Ireland at the time of the Cromwellian settlement.
George Forster Sadleir was commissioned (April 1805) as an ensign in the 47th Foot, without purchase. Promoted to lieutenant in 1806, he took part in the retreat from Montevideo and the unsuccessful attack against Buenos Aires (1807), and was then posted with his regiment to India (December 1807–May 1812). He took part in the expedition against the Joasimi pirates in the Persian Gulf (1809), before being posted to Bombay. In 1812 he was given command of a group of officers and NCOs which was sent to Tabriz in Persia to train the troops of the shah (Fath Ali Shah, 1797–1833). Promoted to captain in 1813, he remained with this military mission until 1815, with the local rank of major. The shah presented him with a sword, and his services were recognised by Lord Hastings (qv), governor-general and C.-in-C. in India.
Returning to India, he took part in the Malwa campaign and was appointed to the political staff of Sir John Malcolm (1817–18). In April 1819 he was chosen by Lord Hastings to carry out a delicate political mission in Arabia. In 1818 Ibrahim Ali Pasha (son of Mohammad Ali Pasha, viceroy of Egypt) had seized the capital of the Wahhabis sect at Dar'iya. The British government knew that Mohammad wished to break away from Turkish control and set himself up as the independent ruler of Egypt. As a result, Sadleir was ordered to travel to Arabia, find Ibrahim Ali Pasha, and present him with a sword and an address congratulating him on his victory. Sadleir was also to propose an alliance against the Qawasimi pirates who were carrying out raids in the Persian Gulf, in the Arabian Sea, and off the Indian coast. He was also under instructions to gather as much topographical information on the interior of Arabia as was possible.
He left Bombay on 14 April 1819, sailing in the East India Company brig-of-war Thetis, and reached Muscat on 7 May. There he unsuccessfully tried to convince the local imam, Sayyid Said, to cooperate with the Egyptian army under Ibrahim. During the next five months he travelled across the interior of Arabia in search of Ibrahim, who he was first told was at Hufuf. On reaching Hufuf, he found that the Egyptian commander was in camp outside Dar'iya; at Dar'iya, that Ibrahim had withdrawn to Rass; and at Rass, that he had moved to Medina. Finally he caught up with Ibrahim at Medina and had audiences with him at Bir Ali, outside Medina, on 8 and 9 September 1819. Ibrahim was non-committal and refused to agree to any joint action against the Qawasimi pirates. Sadleir travelled to Yenbu and from there to Jidda, finally returning to Bombay in May 1820.
While Sadleir was profoundly disappointed at his lack of success, he had carried out an epic journey and was the first European to travel from the east to the west coast of Arabia. Indeed, it was not until 1914 that Capt. W. H. I. Shakespear carried out a similar journey across Arabia, travelling from Kuwait to Aqaba. Also, when one considers that most European maps contained only details of the coastal regions of Arabia, his expedition represented a great advance in geographical terms, as he had gathered a vast amount of topographical information on the country's interior. Indeed, his journal of this expedition remained the only source of information on the interior of Arabia until the early twentieth century. Yet, unlike later travellers such as Sir Richard Burton, C. M. Doughty, and T. E. Lawrence, Sadleir did not see himself as an Arabist and made no effort to adopt local customs and dress, or learn anything of the Arab language.
On his return to India he was appointed as the East India Company's representative in a series of negotiations with the emirs of Scinde (November–December 1820), which concerned the activities of the Cutch and Khosa bandits. He eventually secured a treaty in which the emirs agreed to suppress these bandits while also paying reparations. He served in the Deccan with the 47th Foot (1821–4) and took part in the first Burma war (1824–6). As a brigade major, he was present at the battles of Panlang and Donabew and took part in the storming of the heights of Nepadee. Promoted to major in June 1830, he retired from the army in February 1837.
In 1837 he became sheriff of Cork, and in 1848 married Abigail, daughter of William Ridings of Cork. They had no children. In 1855 he emigrated to New Zealand, where he died 2 December 1859 at Auckland. His diary of his Arabian expedition of 1819 was published after his death as Diary of a journey across Arabia (Byculla, Bombay, 1866).