Left without a family, Tadesse joined his uncle, Beka, as a member of the Arbegnoch, an anti-fascist guerilla resistance movement of Ethiopian patriots who fought the Italian occupation.

In 1942, Tadesse was promoted to the rank of second lieutenant and enrolled into the national military academy at Holota, where he served for years as an instructor.

He was made a commander of the "Fetno-Derash" (Special Forces) and was instrumental in crushing the 1960 coup attempt by proving the conspirators wrong through his loyalty to the Emperor.

[4] Despite initially rejecting the nationalist sentiments that existed among his people, the Oromo, General Tadesse Birru's views were changed during a talk with Prime Minister Aklilu Habtewold.

This is the comment that is believed to have influenced the general's decision to join the Mecha and Tulama Self-Help Association in early 1963, an Oromo social movement in which he went on to become a prominent figure.

[4] His public image helped elevate the association's status and his organizational capacities and leadership qualities transformed the self-help organization into a pan-Oromo movement.

[4] The prime minister used a bombing in Addis Ababa and a rebellion started by Oromos in the Bale province as a pretext to ban the organization.

It was during that time that Tadesse was visited several prominent Oromo leaders such as Baro Tumsa, Elemo Qiltu (Hassen Ibrahim), Ahmad "Hundee" Taqi and the legendary Shaykh Bakhri Saphalo.

[4] He was joined by Colonel Haile Regassa, Major Abebe Gebre Mariam and eventually General Jagama Kello, former military comrades of his.