The establishment of this second Greek state had its origins in the debate over Greece's entry into the war on behalf of the Entente, as advocated by Venizelos, or a Germanophile neutrality as preferred by King Constantine I. This dissension soon began to divide Greek society around the two leaders, beginning the so-called "National Schism". In August 1916, as parts of eastern Macedonia were not defended by the royal government against a Bulgarian invasion, Venizelist officers of the Hellenic Army launched an Entente-supported coup in Thessaloniki. After a brief hesitation, Venizelos and his principal supporters joined the uprising and began the establishment of a second Greek government in the north of the country, which entered the war on the side of the Entente. The National Defence government endured until June 1917, when the Entente powers forced Constantine I to abdicate, and allowed Venizelos to return to Athens as Prime Minister of a unified country. Nevertheless, the establishment of the National Defence government deepened the rift of the National Schism, which would plague Greek political life for over a generation, and contribute to the Asia Minor Catastrophe.