Lots of people join an alliance which they hope will defend them if they get attacked. Others hope for free resources to be shared amongst members. These are “hard power” advantages – you get reinforcements, military actions are launched to support you, weapons for your troops and resources to build your cities are sent your way. That’s all pretty obvious.
And of course “hard power” does come in to play occasionally. For a couple of months now I’ve been watching some of my neighbors (in Dark Blight) having a low-key war with another alliance. Wars happen.
But less obviously, alliances also allow groups of people to cooperate on softer issues.
Example:
About a week ago, the GMs launched a “Mystery” which started with the investigation of some statues, scattered in unspecified spots over the map. Now, the map is huge, and a quick calculation suggests that if I wanted to find all 20 statues, it would take me about 12 hours to survey the entire map looking for these (and if I glanced over one, I’d have to do it again!). Forget it. I’m not doing that. And no doubt the GMs knew that, as an individual, I wouldn’t. But…
I was quite happy to survey the areas around my towns. And so were the other members of my alliance. Within a few hours of the Mystery being announced, we had found most of the statues. Within about a day we had located all 20, and someone had visited each, allowing us to understand what the next steps would be. Alliance Chat and the Messenging system allowed us to swamp ideas, and we posted our findings on the Alliance Forum.
Solving the Mystery still took time. Each player has to visit each site individually (there are 26 in all, and the furthest was over 4 days travel from my Capital). But still, with a week a load of us have finished the mystery and got the shiny prize at the end – though on our own, none of us would have even have attempted it.
That’s the real strength of an alliance. Whatever the GMs throw in (more Mysteries? the rumored Trade v2? another Tournament?) Alliances allow players to cooperate to achieve things that would be beyond them as individuals. It’s not always about hard power – it’s the softer cooperation, too.
The Wisdom of Kurdruk 
Soft power vs hard power is real world political theory. Especially relevant for us when studying P.R China and its relations with the globe. Are you in the field political science?