The excellent blogger Polemarch has recently put up a couple of thought-provoking posts on campaigns. The first talks about types of campaigns, concluding that they are often better in the idea than the execution; the second offers further reasoning about why that might be.
In the ancients era that I usually game and with the types of large set-piece battles I most enjoy, campaigns tend to not have much value. In this era, campaigning was (with one or two notable exceptions) essentially about bringing one's enemy to battle in circumstances least advantageous to them. The battle was had. If the winner was the home team, the invaders were dispersed and the game, so to speak, was up; if the invader was victorious, terms would be reached and the thing was over (unless of course you were fighting the Achaemenid Persians or the Romans, who would [eventually, or fairly immediately, respectively] raise another army and make you do it all again).
The interest then in this era is to try to get battlefield advantage. That is not usually best expressed by manoeuvrings over a campaign map, but by some sort of pre-battle system which modifies morale, numbers, terrain, deployment or leadership to the benefit of one or the other side.
If one is to do this, it is quite useful (as indeed it is for just about any circumstance!) to read Caesar to see the kinds of things he considered important when choosing if or when to give battle.
To me it seems that ancients campaigns work best at either the grand strategic or the tactical level. You can follow the fortunes of nations over years or decades, where competing powers look to prise provinces or regions from one another, or you can follow the fortunes of smaller entities raiding or subduing neighbours in lower intensity local conflicts.
I tried a solo campaign of the latter type set in tribal Iberia. I put quite a bit of time into it, but it simply wasn't exciting enough. It turned out I'd rather refight Zama for the tenth time than try to sustain interest in endless minor encounters between similarly equipped neighbours over local concerns.
For the former type, you can't beat boardgames. If you want to replay the Punic and Macedonian wars, it's far better to do it in a boardgame in one sitting than to stretch it out with questionable bespoke rules to take up three months' worth of miniatures battles, trying to involve players whose chance of winning was, after the first week, only slightly better than nil.
I remember that the time I was most excited about campaigns was back in the Warhammer Fantasy Battle days, when I was young, had oodles of time, and thought that defending a pass against a tidal wave of Orcs was the perfect way to spend a Sunday (and the week before it mulling over army choices!).
The difference here is the difference: you could have Orcs, Goblins, Elves, Dwarves, various humans, all with different characteristics and fighting styles, and all within a realm's distance of one another without doing violence to backstory. Celtiberian tribal dominion versus Celtiberian tribal dominion does not offer quite the same opportunites for variety.
For me, if I want to get six people involved in a game, there are two choices: a boardgame, or a multi-command set-piece battle.
But it's good to be open to being convinced otherwise!
