Tadeusz (Thaddeus) Andrzej Bonawentura Kosciuszko (1746–1817) studied military engineering in Poland and France and traveled to America in 1776 to offer his services to the Continental army. As colonel of engineers he designed fortifications at Philadelphia, Fort Ticonderoga, Saratoga, and West Point and was promoted a brevet brigadier general as the war ended. After returning to Poland, Kosciuszko commanded an army that in 1792 unsuccessfully opposed the second partition of his country, and two years later he led the failed uprising against the Russians that bears his name. He visited the United States briefly, 1797–98, and settled into a life of exile, first in France and from 1815 in Switzerland. Kosciuszko became acquainted with TJ in Philadelphia in 1798, when he gave TJ power of attorney to manage his American assets. Their financial relationship continued in TJ’s retirement, when TJ first loaned himself this money in 1809 and then repaid it in 1815 with part of the proceeds of the sale of his library (ANB description begins John A. Garraty and Mark C. Carnes, eds., American National Biography, 1999, 24 vols. description ends ; DAB description begins Allen Johnson and Dumas Malone, eds., Dictionary of American Biography, 1928–36, 20 vols. description ends ; Miecislaus Haiman, Kosciuszko in the American Revolution [1943] and Kosciuszko, Leader and Exile [1946]; PTJ description begins Julian P. Boyd, Charles T. Cullen, John Catanzariti, Barbara B. Oberg, and others, eds., The Papers of Thomas Jefferson, 1950– , 31 vols. description ends , 30:195–6, 313–5; TJ to John Barnes, 15 June 1809; MB description begins James A. Bear Jr. and Lucia C. Stanton, eds., Jefferson’s Memorandum Books: Accounts, with Legal Records and Miscellany, 1767–1826, 1997, The Papers of Thomas Jefferson, Second Series description ends , 2:1264–5, 1307).

In 1805 Kosciuszko proposed an ecole militaire for the young men of each state to be supervised by members of Congress (Kosciuszko to TJ, [15 Nov. 1805] [MHi]).