The post-war Treaty of Neuilly again denied Bulgaria what it felt was its share of Macedonia and Thrace. After this moment the combined Macedonian-Adrianopolitan revolutionary movement separated into two detached organizations: Internal Thracian Revolutionary Organisation ("bulg." Вътрешна тракийска революционна организация) and Internal Macedonian Revolutionary Organisation. ITRO was a revolutionary organisation active in the Greek regions of Thrace and Macedonia to the river Strymon and Rhodope Mountains between 1922 and 1934. The reason for the establishment of ITRO was the transfer of the region from Bulgaria to Greece in May 1920. ITRO proclaimed its goal as the "unification of all the disgruntled elements in Thrace regardless of their nationality", and to win full political independence for the region. Later IMRO created as a satellite organisation the Internal Western Outland Revolutionary Organisation ("bulg." Вътрешна западнопокрайненска революционна организация), which operated in the areas of Tsaribrod and Bosilegrad, ceded to Yugoslavia. IMRO began sending armed bands called "cheti" into Greek and Yugoslav Macedonia and Thrace to assassinate officials and stir up the spirit of the oppressed population. On 23 March 1923 Aleksandar Stamboliyski, who favoured a détente with Greece and Yugoslavia, so that Bulgaria could concentrate on its internal problems, signed the Treaty of Niš with the Kingdom of Serbs, Croats and Slovenes and undertook the obligation to suppress the operations of the IMRO carried out from Bulgarian territory. However, in the same year IMRO agents assassinated him. IMRO had "de facto" full control of Pirin Macedonia (the Petrich District of the time) and acted as a "state within a state", which it used as a base for hit and run attacks against Yugoslavia with the unofficial support of the right-wing Bulgarian government and later Fascist Italy. Because of this, contemporary observers described the Yugoslav-Bulgarian frontier as the most fortified in Europe.