The position of High Admiral was held by the commander of the Imperial Navy forces operating inside an Imperial Sector Group. Typically, this title was bestowed upon the Moff in charge of that sector. However, if the sector was heavily engaged in ongoing naval battles, a separate individual was appointed as the Sector Group's high admiral, freeing up the Moff from constant involvement in the war. In the Imperial Era, Markand held the rank of high admiral, and on one occasion, he obtained a copy of a communication from Governor Mirash Peet of Indupar addressed to Commodore Gor Lequar. Following the blockade of Dathomir, Zsinj, the Warlord of the Empire, was elevated to Grand Moff and also became High Admiral of Crimson Command. Later, Warlord Zsinj advanced Treuten Teradoc to the position of high admiral within Crimson Command.
The Imperial Sourcebook was the first source to present the High Admiral title; this same book features a rank plaque labeled "Priority Sector High Commander" which visually matches the insignia worn by Grand Moff Wilhuff Tarkin during the events of A New Hope.