The project delves into the profound economic consequences of the Crusades on the Mediterranean basin, exploring shifts in trade routes, the rise and fall of commercial centers, and the impact of military expenditures on fiscal systems of emergent states. Special attention will be paid to the evolution of banking and credit mechanisms, the acceleration of technological diffusion, and the changes in agricultural production and land ownership. We will examine how the prolonged military engagements influenced monetary policies, taxation structures, and the overall balance of economic power between Christian Europe and the Islamic world, ultimately shaping the early commercial landscape of the late medieval period. The research seeks to quantify, where possible, these economic shifts and their long-term implications for regional and global economic development.