At the heart of Brave New World is an increased focus on connections between all the civilizations through Trade, Diplomacy, and Culture. No nation truly exists alone, and a hated enemy can become a temporary ally in the World Congress, or even a trusted trade partner until the bullets start flying. The everyday decisions of managing an empire, no matter the size, are reflected in the changes to basic gameplay concepts and the more dynamic nature of each turn. You have more to do while you wait, and the payoffs increase with skilled management of every facet of your empire.
You need to be more vigilant than ever about the activities of the other civilizations, or you'll find that they've undercut your Culture, all your cities are full of their religious converts, and they've managed to amass enough votes in the World Congress to push through their own agenda. Then there are the ever-present threats of invasion from warlike neighbors and the increased predations of barbarians. You need to use every tool at your disposal to survive, let alone carve out your niche in history!
Barbarians
These savages want nothing more than to prey on your vulnerable units, and now there are more of them than ever before. Encampments spawn at roughly the same rate as they did in earlier versions of the game, but individual camps toss out units a bit faster than they used to.
You'll also notice that barbarians are faster to adapt to technological change, and they have a little more technology as well. It's not a long leap between barbarian Brutes and Swordsmen anymore; they get some axe units in between to give them more teeth.
For a fledgling empire, few things are more frustrating than spending turn after turn building your first Worker or Trade Caravan only to have it immediately taken by barbarian thugs. Even if you shelter your civilian units inside a city, it's dangerous to waste time hiding when you could be out improving your territory. Lost time is almost as bad as a lost unit!
Make sure to send out guards with your Workers, and keep a few Archers on the hills as lookouts. If you've got a more spread-out empire, mounted units have the movement to get to the problems and the strength to hold out until the stronger infantry can get there.
Even the least militant empire may want to spend a point in the Honor policy so you don't get blindsided by barbarian encampments appearing without warning. You get a combat bonus to make sure that you don’t require a large defense force to stamp them out. Barbarians used to be a pest that you could ignore or use as fodder for green troops to get a taste of combat (or as supplemental units for the Germans). Now they’re a real threat to your interests if left unchecked because they lay waste to undefended Trade Routes.
City-States
City-States always present interesting choices. Do you annex them and add them to your empire, turn them into puppets with a veneer of independence, use them for their resource potential, or keep them around for votes on the World Congress? These are the questions you have to ask yourself as you foster relationships with the independent City-States around your civilization.
City-States are beneficial for trade, as you can make steady money without fear of losing your research edge, like an International Trade Route with another civilization. If you keep them as an Ally, they'll give you an extra vote in the World Congress, but if you take them over that vote goes away. That said, if they're teetering on the edge of Allying with another civilization, taking them over would be better in the long run as you surely can't let someone else get that precious vote! Civilizations pursuing Cultural Victory need to make these hard choices, as keeping City-States as Allies will occasionally net you gifts of Great People. When you are working to fill your Museums and Wonders with Great Works of Art, Writing, and Music, every Great Person you can get is a treasure.
Once in a blue moon an Allied City-State might even send you a Great Person that is usually exclusive to Venice (a Merchant of Venice). These unique Great Merchants can buy a City-State outright. If a City-State sends you one, maybe they are trying to send you a message.
Intrigue
Spies are more difficult to balance now. In Brave New World, you get to use these resources in a new way. They can still defend your Technology or steal it from other nations, but they can also turn into Diplomats. This eventually earns you additional votes to control late-game Diplomacy, and it's a useful way to see what other people are doing in their cities without the risk of harming relations.
Diplomats are spies in plain sight. They inform you how other people are going to vote. And, you can watch carefully over your neighbor's Capitals to see what type of victory they're pushing toward. If they are going after numerous cultural Wonders, make sure you've got enough Culture to combat their Tourism. If they are strengthening their defenses, edge them out technologically. If they are sending expeditionary forces, pressure them diplomatically and make them pay economically. Every bit of intelligence your Spies can pull in is another way to make sure that your civilization stays supreme, or it gives you the edge to come from behind and hit them in a way they didn't see coming!
