The designation High General signified a high-ranking role within the Imperial Army. Typically, a High General had control over a Systems Army, which was primarily an administrative command level directly under the Surface Marshal who oversaw a Sector Army. This Systems Army consisted mainly of a headquarters staff focused on coordinating Corps and Armies on the front lines. They also monitored resource availability within the sector to facilitate deployment in support of field formations when needed. They were sometimes referred to as Commander.
However, the title of High General wasn't exclusive to the Imperial military. Prior to the Clone Wars, Bycha held the title of High General as the military leader of Typha-Dor. During the Clone Wars, the Jedi Generals who commanded the ten Systems Armies within the Grand Army of the Republic were given the rank of High Jedi General. These Jedi Generals can be seen as precursors to the Imperial Army's High Generals, though the role's significance may have changed significantly under the Empire, particularly regarding the organization of the associated Systems Army. The Rebel Alliance also used the title during the Galactic Civil War. Furthermore, Ajunta Pall, the leader of the Dark Jedi, used the title as far back as the Hundred-Year Darkness.
The Imperial Sourcebook mentions the High General title briefly in a single paragraph. It describes them as officers ranking above Generals who command standard field Armies of four Corps, but below the Surface Marshal, who is either the local Moff or a designated commander overseeing all Imperial Army activities within their sector. The authors may have envisioned two High Generals within a Sector Army. However, the text could also imply a single High General acting as an administrative assistant to the Surface Marshal, or a varying number depending on the forces deployed.
A further complication arises when trying to understand the exact meaning of "High General." According to the hierarchy in the Imperial Sourcebook, a High General is implicitly equivalent to a Fleet Admiral in the Imperial Navy. Despite the similar names, the Navy rank of High Admiral corresponds to the Surface Marshal. It remains unclear whether these positions are true hierarchical ranks or simply titles indicating specific levels of senior command, held in addition to substantive ranks.
These difficulties in understanding the precise role and status of a High General in the Imperial Army are exacerbated by the scarcity of explicitly identified High Generals in canon sources. The only clear example is High General Sutt Ramic, who commanded one of the three Golan III battlestations protecting Muunilinst in 19 ABY. He was described as the senior military officer stationed at the financial center of Imperial Space. It is uncertain whether Ramic's seniority stemmed from his rank or a specific commission. If the latter, it raises questions about whether his command was limited to Muunilinst's defenses or its star system, or if it extended across a wider area. Even if these questions could be answered, it would still be necessary to determine if the command structure at Muunilinst was representative of Imperial Space as a whole and whether the hierarchy at that time aligned with the models from twenty years prior.