Ludwig Karlovich Martens spent his childhood and youth in Russia. In 1899, sent abroad by the tsarist authorities as a "politically unreliable foreigner," he left for Germany, then for England America. Repeatedly repressed by the Russian, German, English and American police, he proudly said about himself that he remained a revolutionary everywhere, but "wherever I was, my life was in the Russian revolutionary movement and only in it." About the life and activities of the old Bolshevik L. K- Martens, member of the Lenin Union of Struggle for the Liberation of the Working Class, diplomat, talented inventor and engine engineer, professor, doctor of technical sciences, is described in this essay.