|This article relies largely or entirely on a single source. (May 2016)|
Cesarec was born in Zagreb, which was part of Austria-Hungary at a time. As a high school student he was involved in radical nationalist politics and joined the group that tried to assassinate Croatian ban (viceroy) Slavko Cuvaj. For his role in failed assassination he received two years of prison sentence, which he served in Sremska Mitrovica penitentiary. There he began to study books of Stirner and Kropotkin, which gradually led him to adopt Marxist philosophy. From 1915 to 1918 he served in Austro-Hungarian Army and experiences of World War I made him into an enthusiastic supporter of October Revolution and Communism.
After the war he became a member of the Communist Party of Yugoslavia. Because of that he often had to deal with police and emigrate to Prague, Vienna, Moscow and Spain, where he spent some time during Spanish Civil War.
Cesarec, who had discovered his literary talent in teenage years, was also known as one of the leading Croatian literary figures of his time. He wrote poems, plays, short stories and novels and participated in literary magazines run by Miroslav Krleža. In March 1941, a few days before the Axis invasion of Yugoslavia, he was arrested and interned in Kerestinec prison together with some 90 leading members of Croatian left-wing intelligentsia. Few weeks later the prison was taken by new Ustasha regime. On 9 July, the Ustashas had ten prisoners, including Božidar Adžija, Otokar Keršovani and Ognjen Prica, shot as retaliation for Partisan activities. Fearing the rest of the inmates would be shot soon afterwards, Croatian Communist Party organised a prison-break on the night of 13 July. The prison guards were overtaken and inmates escaped. But the operation proved to be poorly organised and most of the prisoners, including Cesarec, were quickly recaptured and shot in Maksimir woods few days later.
- "August Cesarec". hrt.hr (in Croatian). Retrieved 21 January 2016.