After the St Nedelya Church assault in April 1925, he became increasingly radical and active in anti-government groups. He came into contact with Vasil Popov, with whom he created an anti-government guerrilla group of anarchists and communists "Guéroïa". In 1924 and 1925, many anarchist groups fled to the west, but Simov and Popov remained in Bulgaria. On November 23, 1925, Simov led an attack on the city governments of the villages of Balgarene and Kazachevo. In 1927, they attempted to rob the Zemedelska Bank in Troyan. In the ensuing firefight Popov, heavily wounded, reputedly killed himself in order to avoid capture. Simov escaped. In 1928 Simov became the head of another small group of anarchists and communists. Pressured by police prosecutions, the group fled to Yugoslavia. In the ensuing years, Simov traveled throughout Europe, searching for connections with other anarchist organizations. In 1934 he returned to Bulgaria and made attempts to resurrect his activities without much success. There are multiple accounts of his death. In one, he hid for some time in the village of Lomec, Troyan. In 1935 his hideout was surrounded by the police, but heavily wounded he still managed to escape. He came back to Balgarene, where he hid in a barn for several days. After a betrayal, the police yet again surrounded Simov and during the firefight he killed himself. In another, he was killed by Stalinists after they took power in 1944. There was a photograph of a cadaver reproduced in the press of that time and said to be Simov, but that may have been the body of one of Simov's collaborator.