[2] At about the same time, he was appointed comes excubitorum (Commander of the Excubitors, the imperial bodyguard), and in 584, he replaced John Mystacon as magister militum for the East, thus becoming responsible for the conduct of the ongoing war against the Sassanid Persians.

[1] He commanded numerous raids into Persian territory in 584–585, ravaging the plains near Nisibis,[1] and making inroads in the regions of Arzanene and eastern Mesopotamia.

[3][5] When Priscus arrived in the East, however, the soldiers refused to obey him, and elected the dux of Phoenice Libanensis, Germanus, as their leader in his stead.

[6] After a public reconciliation with his troops, in the summer of 589 he campaigned against the city of Martyropolis, which had recently fallen to the Persians through the treacherous defection of a Roman officer named Sittas.

Philippicus failed to retake it and was defeated by a Persian relief force led by Mahbodh and Aphrarat, after which he was replaced by Comentiolus.

[6][7] Except for a diplomatic mission in 590 to the recently deposed Persian ruler Khosrau II (r. 590–628), who had taken refuge in Roman territory, Philippicus disappears from the scene for several years.

[2] As one of the leading generals of his day, and with both the time and opportunity to write it sometime after 603, during the years he spent in a monastery, Philippicus is one of the possible authors of the military treatise known as the Strategikon and traditionally attributed to Maurice.