Since it was founded, Slitherine has been producing a series of excellent wargames with both a strategic component that covers an entire war on a province level, and a tactical component that involves battles of large numbers of soldiers in a 3D representation. Legion has been one of their most successful titles, perhaps because it covers a huge period of Roman history, with 20 something scenarios and 3 complete campaign games, along with extensive diplomatic rules to cover relationships with other powers that can affect the outcome of a war. If you're interested in the period, it's well worth looking into.
Maybe.
I actually bought this game some years ago, for a very low price. It looked like it was going to be nice and addictive, and that I would spend hours playing it. I didn't.
I started playing campaign, or a scenario, can't remember, as the ruler of a province of England. I easilly managed to conquer the neighboring provinces, and sealed some alliances (one, in fact, if I correctly recall).
So, it was good, I was developing my cities, conquering others, developing them too, and so on...
Then it started to freeze. Not the software, but the situation. My enemies had become as powerful as i was, and even with fully experienced and balanced armies, I never managed to defeat them, and they never manged to defeat me.
So right after that, I uninstalled the game, and never played it again. But maybe it was just me, the specific setting of that scenario, the way I played, I don't know.
Still, I must admit, I always enjoyed planning battles, as you can give quite simple but very effective directions to your troops. Well, it started to really bore me after the 100th, but, yeah, that part was good.