Angelov was born in 1900 in the city of Kyustendil to a mason father and a weaver and laundress mother, both Bulgarian refugees from Macedonia. In 1923 he married Aleksandra Sharlandzhieva; the two had a daughter, the writer Svoboda Bachvarova (b. 1925). Angelov was related to the anarchist left wing of Internal Macedonian Revolutionary Organization (IMRO) and the Bulgarian Communist Party from an early age; in 1923 he took part in the failed and suppressed September Uprising, more specifically in its Pirin Macedonia operations. After the communist St Nedelya Church assault of 1925, he was sentenced to death but managed to escape the country with his family.