The purpose of the article is to find out the biography of Maksym Kryvonis at the beginning of the Cossack uprising of 1648, the campaign on the territory of Podillia and South-Eastern Volyn, its course, military actions, the political self-awareness of the participants of the expedition and its consequences for the development of the Ukrainian National Revolution in the summer of 1648. The methodological foundation is based on the concepts of the "Annals" and "New Social History" schools, as well as the principles of historicism, objectivity, reliance on historical sources, systematicity, and comprehensiveness. The main research methods were narrative, reconstructive, chronological, comparative, historical-genetic, and synchronous. The scientific novelty lies in an attempt for the first time in historiography to reconstruct a complete picture of the liberation campaign of M. Kryvonis in Podillia and South-Eastern Volyn, the program requirements of its participants, and the military-political consequences for the development of the revolutionary struggle in the summer of 1648. Conclusions. The study of the discovered complex of sources and scientific literature gives reason to see M. Kryvonis as an outstanding leader of the national liberation, religious and social struggle of the population of Right-bank Ukraine, which began to transform into the National Revolution. The campaign began at the end of the first decade of June with his capture of Pogrebyshchi and ended at the end of July with B. Khmelnytsky’s recall to his camp. It went through two stages in its development: the 1st (approx. June 7-8 - early July) was marked by successful military actions with Polish hostages in the cities of Bratslav Region and the liberation of its territory from Polish rule; The 2nd (beginning of July - end of July) was mainly characterized by the struggle with magnate and government units, which ended with the successful battle of Starokostiantyniv on July 26-28, the retreat of the troops of Prince I. Vyshnevetskyi and the liberation of the territories of Southwestern Zhytomyr region and Southeastern Volyn. Thanks to his military and organizational talents, M. Kryvonis managed to transform the 400-th Cherkasy regiment at the beginning of the campaign into a 28-30-thousand-strong army at the time of its completion. Fully sharing the revolutionary sentiments of the Cossack commoners, who sought liberation from national-religious oppression and social subjugation, to achieve personal freedom, land ownership, and independence of Russia ("on the Vistula") from the Polish Crown, he became the informal leader of a radical group of elders, which transformed into the Ukrainian political proto-elite.