Hungary did not abandon the idea of reuniting the "Lands of the Crown of Saint Stephen" after the Treaty of Trianon. Based on this doctrine, Hungary sought the revision of the treaty, claiming territories from Czechoslovakia, Romania and Yugoslavia, including regions with no significant ethnic Hungarian population, such as Croatia. Between 1938 and 1940, following German–Italian mediation in the First and Second Vienna Awards, and the Hungarian invasion of Carpatho-Ukraine, Hungary enlarged its territory. It absorbed parts of southern Czechoslovakia, Carpathian Ruthenia and the northern part of Transylvania, which the Kingdom of Romania ceded. One of the ethno-cultural areas that changed hands between Romania and Hungary at this time was the Székely Land. The support that Hungary received from Germany for these border revisions meant that the relationship between the two countries became even closer. On 20 November 1940, Hungary formally joined the Axis Tripartite Pact.