[2][3] Belli was repeatedly prosecuted and sentenced to prison for his political views, and was altogether imprisoned for 11 years, and forced into exile for another 18.

Belli was born in 1916 in Silivri, then in the Ottoman Empire, to Mahmut Hayrettin Bey, later a prominent leader of the Turkish War of Independence in Urfa.

He was educated at Robert College in Istanbul, and in 1936 went on to study economics at the University of Mississippi in the United States.

The government, under the influence of the German advances in the initial years of World War II, had abandoned its policy of friendship with the USSR.

Belli left Turkey in 1946, and joined the Greek Civil War as a guerrilla fighter on the communist side.

He was part of the group who published the revolutionary magazines Türk Solu and Aydınlık Sosyalist Dergi.

At this time, he developed his well-known thesis known as Milli Demokratik Devrim (National Democratic Revolution), abbreviated MDD.

[7] With his friends, Belli contacted Deniz Gezmiş and Mahir Çayan, who were at the time leaders of the youth movement amassing popular support.

The ideas of MDD quickly gained prominence among the leftist youth movement; it became the main theoretical framework for most of the leftist groups that flourished in Turkey in that period[8] and played a key role in the '68 movement in Turkey, giving it a Marxist and revolutionary characteristic.

[9] Mihri Belli left Turkey after the 1971 military coup to avoid arrest, and was for a while a guest of the Palestine Liberation Organization.