Klapka was born at Temesvár, Kingdom of Hungary (nowadays Timișoara, Romania) and entered the Austrian Army in 1838. He was still a subaltern when the Hungarian Revolution of 1848 broke out, and he offered his services to the patriot party.
He served in important staff appointments during the earlier part of the war which followed; then, early in 1849, he was ordered to replace Lázár Mészáros, who had been defeated at Kassa, and as general commanding an army corps he had a conspicuous share in the victories of Battle of Kápolna, Isaszeg, Vác, Nagysalló and Battles of Komárom. Then, as the fortunes of war turned against the Hungarians, Klapka, after serving for a short time as minister of war, took command at Komárom, from which fortress he conducted a number of successful expeditions until the Surrender at Világos (now Şiria, Romania) in the August put an end to the war in the open field. He then defended Komárom for two months, and finally surrendered on honorable terms.
Klapka left the country at once, and lived thenceforward for many years in exile, at first in England and afterwards chiefly in Switzerland. He continued by every means in his power to work for the independence of Hungary, especially at moments of European war, such as 1854, 1859 and 1866, at which an appeal to arms seemed to him to promise success. In 1859, Alexander John Cuza, the first Ruler of the United Principalities of Wallachia and Moldavia, offered general Klapka military support asking for a favourable reconfiguration of other peoples' situation in the Habsburg Empire (including Romanians): ”In May 1859 two agreements were signed between Alexandru Ioan Cuza and general Klapka, commander of the Hungarian revolutionaries, by which A.I. Cuza commits to obtain and provide weapons to Hungarian revolutionaries, helping them against Austria, at the same time setting the principles for reconciliation between the nationalities of Austria.”
After the war of 1866 (in which as a Prussian major-general he organized a Hungarian corps in Silesia), Klapka was permitted by the Austrian government to return to his native country, and in 1867 was elected a member of the Hungarian Chamber of Deputies, in which he belonged to the Deák party. In 1877 he made an attempt to reorganize the Turkish army in view of the war with Russia. General Klapka died at Budapest on 17 May 1892. A memorial was erected to his memory at Komarom in 1896.
He wrote Memoiren (Leipzig, 1850); Der Nationalkrieg in Ungarn, &c. (Leipzig, 1851); a history of the Crimean War, Der Krieg im Orient . . . bis Ende Juli 1855 (Geneva, 1855); and Aus meinen Erinnerungen (translated from the Hungarian, Zurich, 1887).
- Obituary, New York Times, May 18, 1892 p. 4
- One or more of the preceding sentences incorporates text from a publication now in the public domain: Chisholm, Hugh, ed. (1911). . Encyclopædia Britannica. 15 (11th ed.). Cambridge University Press. p. 844.
- C.C. Giurescu (ed.), 1972, Romania's History in Data, Bucharest, Romanian Encyclopedic Publishing, p. 207