Jan Gotlib "Bogumił" Bloch (Russian: Иван Станиславович Блиох or Блох; 24 July 1836 – 7 January 1902) was a Polish banker and railway financier who devoted his private life to the study of modern industrial warfare. Born Jewish and a convert to Calvinism, he went to considerable lengths to oppose the prevalent antisemitic policies of the Tsarist government in Congress Poland, and was sympathetic to the fledgling Zionist movement.

Bloch had studied at the University of Berlin, worked at a Warsaw bank and then moved to Saint Petersburg, capital of the Russian Empire (which governed much of the Polish lands at the time). There, he took part in the development of the Russian Railways, both in financing the construction of new railways and in writing research papers on the subject. He founded several banking, credit and insurance companies. In 1877, he was appointed a member of the Russian Finance Ministry's Scientific Committee.

Bloch was married to Emilia Julia Kronenberg H. Koroniec (1845–1921), the granddaughter of Polish banker Samuel Eleazar Kronenberg, daughter of medical doctor Henryk Andrzej Kronenberg and niece of industrialist and Polish nationalist Leopold Stanisław Kronenberg; the Kronenberg and Bloch families had often been in competition with each other in several 19th-century Polish businesses.

Born in Radom, Poland, on 24 July 1836, Bloch became intrigued by the victory of the North German Confederation over France in the Franco-Prussian War of 1870–1871, which suggested to him that the solution of diplomatic problems by warfare had become obsolete in Europe. He published his six-volume master work, Budushchaya voina i yeyo ekonomicheskie posledstviya (Russian: Будущая война и её экономические последствия, Future War and its Economic Consequences), popularized in English translation as Is War Now Impossible?, in Paris in 1898.

His detailed analysis of modern warfare, its tactical, strategic, and political implications, was widely read in Europe. Bloch argued that:

Bloch attended the first Hague Peace Conference in 1899, possibly at the invitation of Tsar Nicholas II, and distributed copies of his work to delegates from the diplomatic missions of 26 states, to little avail. The British publicist W. T. Stead also worked to spread Bloch's insights. In each particular, Bloch's theoretical research was rejected or ignored. To the British readers of The Contemporary Review, Bloch wrote in 1901:

Having busied myself for over fourteen years with the study of war in all its phases and aspects, I am astonished to find that the remarkable evolution which is rapidly turning the sword into a ploughshare has passed almost unnoticed even by the professional watchmen who are paid to keep a sharp look-out. In my work on the war of the future I endeavoured to draw a picture of this interesting process. But writing for specialists, I was compelled to enter largely into details, the analysis of which ran into 3,084 pages. The facts which are there garnered together, and the consequences which flow from them, run too strongly counter to the vested interests of the most powerful class of the community to admit of their being immediately embodied in measures of reform. And this I foresaw from the first. What I could not foresee was the stubbornness which [it] not only recoiled from taking action but set itself to twist and distort the facts. Patriotism is highly respectable, but it is dangerous to identify it with the interests of a class. The steadfastness with which the military caste clings to the memory of a state of things which has already died is pathetic and honourable. Unfortunately it is also costly and dangerous. Therefore I venture now to appeal to the British masses, whose vital interests are at stake and whose verdict must be final.

Europe's patriots were unmoved. French cavalry and British infantry commanders only learned Bloch's lessons by a process of trial and error once Bloch's impossible war, World War I, had begun. The Russian and German monarchies proved equally incapable of assimilating Bloch's cautionary words concerning revolution, paying the price with summary execution and exile, respectively.