Mezue ahịrịokwu na-esonụ: Clarke bụ otu n'ime ndị ọchịagha Franco-Irish kachasị nwee mmetụta na nke nwere mmụọ na ndị agha France n'oge Napoleon. O nwere njikọ chiri anya na Irish Brigade nke France. Nna ya jere ozi na Dillon's Regiment (ebe Clarke n'onwe ya jere ozi nwa oge) na nna nne ya na ọtụtụ ndị nwanne nna ya jere ozi na Clare's Regiment. Site na ntiwapụ nke French Revolution, Clarke jere ozi na mmalite French Revolutionary Wars na ndị agha nke Rhine, na site na 1793 e buliri ya n'ọkwá "général de brigade". N'afọ 1795, e jidere Clarke ruo nwa oge. Mgbe a tọhapụsịrị ya, Clarke biri na Alsace ruo mgbe Lazare Carnot zigara ya Ịtali ije ozi dị ka onyeisi ndị ọrụ topographical nke Napoleon Bonaparte, ruo mgbe e zigara ya na Sardinia. Mgbe 18 Brumaire gasịrị, Clarke jere ozi dị ka Onye isi nke Bureau Topographical, Councillor State, odeakwụkwọ steeti maka ndị agha na ndị agha mmiri. N'oge agha megide Austria n'afọ 1805, a họpụtara Clarke ka ọ bụrụ gọvanọ nke Vienna na n'oge agha ahụ.
agha megide Prussia na 1806 ọ rụrụ ọrụ dị ka gọvanọ nke Erfurt na Berlin.