One year after Boris's accession, Aleksandar Stamboliyski (or "Stambolijski") of the Bulgarian Agrarian National Union was elected prime minister. Though popular with the large peasant class, Stambolijski earned the animosity of the middle class and military, which led to his toppling in a military coup on 9 June 1923, and his subsequent assassination. On 14 April 1925, an anarchist group attacked Boris's cavalcade as it passed through the Arabakonak Pass. Two days later, a bomb killed 150 members of the Bulgarian political and military elite in Sofia as they attended the funeral of a murdered general in the St Nedelya Church terror assault. Following a further attempt on Boris's life the same year, military reprisals killed several thousand communists and agrarians, including representatives of the intelligentsia. Finally, in October 1925, there was a short border war with Greece, known as the Petrich incident, which was resolved with the help of the League of Nations.