He was against foreign intervention by the Great Powers in Southeast Europe, believed in a Balkan Federative Republic and opposed Bulgaria's military engagements in the Second Balkan War and First World War. A deputy to the National Assembly of Bulgaria, Blagoev voted in October 1914, along with the rest of the faction of narrow socialists, against war credits. During World War I as deputy Blagoev exposed "the war’s imperialist nature and the "traitorous role" of the Second International". Blagoev hailed the Russian October Revolution and propagandized for the ideas of the Bolsheviks. Under his leadership the Narrow Socialist party broke with the Second International. In a speech before the Bulgarian National Assembly in 1917, Blagoev called himself "Macedonian Slav". In a Declaration against the Treaty of Neuilly, read by Dimiter Blagoev in the Bulgarian National Assembly in 1919 he protested against the partition of the Bulgarian land and nation and promoted the ideas of the Bulgarian Soviet Socialist Republic, as a part of a Balkan Federal Soviet Socialist Republic, as the only political solution able to assure freedom of Macedonia, Thrace and Dobruja and as a counterweight of Bulgarian nationalism.