Distance marching rates, infantry v cavalry

[D B Campbell]

Furthermore Gallienus' force at Milan was between 50 and 60 alae (Cheesman 1941) so 25,ooo troopers (that's a LOT of fodder and a massive muck heap for the horses!) to be dispatched as required.

I think someone's been pulling someone else's leg. Cheesman (1914) covers "the auxilia during the first two centuries AD" (p. 21), so naturally he doesn't discuss Gallienus. Like the "Fate of the Ninth Legion", Gallienus' "Battle cavalry" grows with each retelling. I'd be intrigued to discover the source of this particular elaboration! :-)