Kassa Hailu, born into a country rife with civil war, had defeated many regional noblemen and princes before becoming Emperor of Ethipia during time known as the Zemene Mesafint or "Age of the Princes".

During this era, regional princes, and noble lords of diverse ethnic and religious backgrounds have vied with each other for power and control of the Gondarine Emperor.

A puppet Emperor of the Solomonic dynasty would be enthroned in Gondar by one nobleman, only to be dethroned and replaced by another member of the Imperial dynasty when a different regional prince was able to seize Gondar and the reins of power.

Regions such as Gojjam and Shewa are ruled by their own branches of the Imperial dynasty and, in Shewa, the local prince goes as far as assuming the title of King.

In Wollo, competing royal powerful Oromo and Muslim dynasties also vie for power.

Nevertheless, a semblance of order and unity has been maintained in northern Ethiopia during the era of the Princes by the powerful rases of the Were Sheik dynasty of Wollo such as Ras Ali the Great and Ras Gugsa who control Gondar and the Emperor.

Kassa had begun his career in this era as a shifta (outlaw), but after amassing a sizable force of followers, had been able to not only restore himself to his father's previous fief of Qwara but had been able to control all of Dembiya.

Moreover, he had gained popular support by his benevolent treatment of the inhabitants in the areas he controls.

This had garnered notice of the nobleman in control of Gondar, Ras Ali II of Yejju of Wollo.

Empress Menen Liben Amede, wife of Emperor Yohannes III, and the daughter of Ras Ali had arranged for Kassa to marry her granddaughter, Tewabech Ali.

She had awarded him all of Ye Meru Qemas in the hopes of binding him firmly to her son and herself.

Although all sources and authorities believe that Kassa truly loved and respected his wife, his relationship with his new in-laws deteriorated largely because of the disdainful treatment he repeatedly received from the Empress Menen.

By 1852, he had rebelled against Ras Ali and, in a series of victories—Gur Amaba, Takusa, Ayshal, and Amba Jebell —over the next three years he had handily defeated every army the Ras and the Empress sent against him.

At Ayshal he had captured the Empress Menen, and Ras Ali had fled.

Kassa had announced that he was deposing Emperor Yohannes III, then marched on his greatest remaining rival, Dejazmach Wube Haile Maryam of Semien.

Following the defeat of Dejazmach Wube, Kassa is crowned Emperor by Abuna Salama III in the church of Derasge Maryam on February 11, 1855.

He takes the throne name of Tewodros II, attempting to fulfill a prophecy that a man named Tewodros will restore the Ethiopian Empire to greatness and rule for forty years.

Tewodros had refused to acknowledge an attempt to restore the former Emperor Sahle Dengel in the place of the hapless Yohannes III, who had acknowledged Tewodros immediately.

Yohannes III is treated well by Tewodros, who seems to have had some personal sympathy for him.

His views on Sahle Dengel are not known but are not likely to have been sympathetic.