Amateurs in command?

[D B Campbell]

Some authors believe there was a class of "viri militares" which had a special cursus.

Basically a misunderstanding, I believe. Tacitus uses the phrase to refer to primipilares (time-served centurions who had risen to the post of primus pilus before embarking on a higher equestrian career). These were definitely the "military men" of the empire.

The main problem is that we have no idea whether any system of selection was applied at any stage of the senatorial cursus. There certainly doesn't seem to have been any selection, in the sense that we would apply it today. On the contrary, the emperor's legates were gentlemen officers (like Wellington and Marlborough) who were expected to be naturally talented. Some were. Some were not.