The primary reason for the fall of the Ottoman Empire was its inability to modernize and adapt to changing political, social, and economic conditions. By the late 19th and early 20th centuries, the Empire was plagued by internal strife, nationalist movements among various ethnic groups, and military defeats, especially during World War I. These challenges were exacerbated by the Empire's failure to industrialize effectively, resulting in economic decline and inability to compete with European powers. The war led to significant territorial losses and the eventual partitioning of Ottoman lands, culminating in the establishment of the Republic of Turkey in 1923.