in 1912, greece took part in the balkan wars, where it gained many of the territories that make up the country now, such as greek macedonia and the islands of the aegean sea. greece fought in both world war i and world war ii in the side of allies. during world war i, greece was divided into two countries, the state of thessaloniki in the north and the state of athens in the south. both countries claimed to be the legitimate government of greece, but the state of thessaloniki received support from the allies. the country was reunited in 1917 when the king abdicated. in 1920 greece expanded again and briefly reached its maximum size. the territories that the country had gained in turkey were given back to turkey in the 1923 treaty of lausanne, but greece kept western thrace. the king returned in 1935, and greece was under a fascist dictatorship from 1936 until 1941, friendly to the allies when it was invaded by nazi germany.