The decline of the Ottoman Empire in the 20th century was prompted by a range of changes, including internal strife, military defeats, and the rise of nationalism among subject peoples. The empire faced significant challenges during World War I, aligning with the Central Powers and ultimately suffering severe territorial losses. The war accelerated nationalistic sentiments, leading to the emergence of independence movements in territories such as Greece, Serbia, and the Arab lands. Furthermore, European powers exploited the empire's weakness, resulting in significant territorial divisions during the Treaty of Sèvres in 1920. This culminated in the establishment of the Republic of Turkey in 1923.