On Towards the Stars: Executing a Diplomatic Victory
[This post is part of a larger strategy guide for Civilization 6]
Diplomatic victories are simultaneously some of the easiest and some of the hardest victories to get.
The actual mechanics of getting a diplo victory are really straightforward. You have 20 points that you need to get, they come up for grabs at very specific intervals, you upvote the relevant policies and you try and survive the rest of the time.
In practice, in a multiplayer game where every other player is human, getting a diplo victory can be really hard. That's because the mechanics of the diplo victory are such that everyone else in the game can pile against you to slow or stop your progress without going to war or incurring significant costs.
Every time someone has won a diplo victory in one of my games, it's either come as a surprise or the player had a dominant position along most axes and was just ending the game as quickly as possible.
When to choose Diplo
To a first approximation, you can't win a diplomatic victory until at least the atomic age. The relevant points just don't become available soon enough. So the first thing you have to consider is whether the game will even go on that long. If someone is going to win on culture, religion, or domination beforehand, spending a lot of resources going for diplomatic victory points is just going to hurt you.
You can't really win a diplo victory without getting a lot of diplomatic favor. That in turn is most easily generated by being suzerain of a lot of city states. So the next question you should be asking is whether enough city states exist in the game for you to win. There's no hard and fast rule here, but I think you need at least 6 city states in the game to really solidly guarantee a diplo victory.
If both those conditions are met, you want to think about a stack of things: how likely are you to get the relevant wonders? How many suzerains can you hold onto of the remaining city states? Are you well set up to win whatever emergencies come up?
Civs that do well for diplo victories are those that have natural bonuses towards city states (Hungary, Greece), get bonuses for diplo favor (Canada), or have the ability to trigger additional "special events" (Sweden).
20 to win
"20 to win". This should be your mantra for the entire game, or at least as soon as you decide to go for a diplo win. You should constantly be thinking about where your 20 points are coming from and how quickly you can guarantee it. The earlier you can win, the better — winning on Diplo can be very tough once nukes are flying.
There are 7 points that are up for grabs through wonders:
2 for Mahabodhi Temple;
one for Potala Palace;
4 for Statue of Liberty.
You want to get all of them, so rush the relevant wonders if necessary. Basically no one builds Statue, but Mahabodhi is useful for religious players and Potala is useful for everyone, so expect some competition.
At the first two World Congress sessions (starting in the Medieval era), you can win an additional 2 points by voting for winning policies. At every World Congres starting in the Modern era, you have an additional potential to gain or lose 2, for a net difference of +4/-2. World Congress comes around once every 20 turns (on quick speed), and there are roughly 3-4 World Congress sessions before the modern era.
If you get every relevant wonder, you still need 13 points to win, which means you need to wait for 5 World Congress sessions at minimum, sweeping all of them (you need to win 2 + 2 + 2 + 4 + 3). Put bluntly, this is very hard if someone realizes what you're doing. Still, World Congress is the primary way to get diplo victory points; I think you should aim to get at least 8-10 more from voting alone.
That leaves you with 3-5 more points to scrounge up. The rest of them will have to come from events like aid requests (+2 if you win) and scored competitions (+1 each).1
For the most part, your game plan is pretty fixed. The only remaining question is how to maximize your diplo favor so you can more easily win points from the Congress.
Pokerface
You want to avoid making it obvious that you're going for a Diplo victory. Like I said, a solid chunk, maybe even the majority of Diplo wins I've seen have been a total surprise. The best way to do that is to burst a ton of diplomatic victory points in a very short time span, so that you're much closer to winning than the scoreboard may make it seem. And the best way to do that, in turn, is to carefully set up a massive foundation of diplomatic favor so that you can opportunistically sweep a World Congress.
A really common way to sneak a Diplo win is to:
Start building Statue of Liberty but leave it unfinished with one turn left;
Wait for a World Congress, sweep it, net 4 points;
Finish Statue, net another 4 points.
This is an 8 point swing in basically no time at all, there's nothing your opponents can do. And you can make this even more aggressive by chaining or timing your burst with a win on some scored competition, which can give you a +9 or +10 point swing in one shot.
The most tricky part of all this is actually being able to sweep a late game World Congress. You ideally end up in a situation where you can single handedly win every resolution, even if everyone else opposes you. That requires a lot of Diplo favor.2
Ideally, you spend the entire game hoarding favor, spending basically none of it until a final sweep. But you still need to win resolutions! So in the first few World Congress meetings, you're going to have to politic your way to the winning coalition. Most of the time, this is pretty easy — in the Medieval and Renaissance era, there are rarely resolutions that make a massive difference in the game, so most everyone is willing to work together to vote for the same thing. When that doesn't happen, make sure you have a sense of who cares about the outcome so you can vote accordingly.3 Don't be afraid to make deals — up to and including going to war — if it means you'll get a coveted victory point without spending any favor.
When you're not playing the table, you should be thinking about how to get and keep suzerains and improve your diplomatic favor generation.
Go hard for things that get envoys or boost suzerain bonuses — you want to get Apadana (+2 envoys per wonder built in the city), Monarchy (+50% influence points), Kilwa (+3 envoys when built and massive bonuses for being suzerain, you always want this), Országház (+100% Diplo favor for each suzerain you have), and a fully decked out Diplomatic Quarter.
You also want a cabal of spies that can run "Fabricate Scandal" over and over, and as many alliances as you can get.
Common mistakes
The biggest problem with a diplomacy focused strategy is that it leaves you really vulnerable to just falling behind. Investing in science or culture has knock on effects that benefit your overall civ — you become more resilient to attack, get stronger units, and generally preserve optionality. You can pivot from science to military or from culture to religion, production generally doesn't get wasted. But if you invest a lot in diplomacy, it doesn't really pay the same dividends.
Just think about diplomatic favor, as a construct. In an all-human game, it's only use is to win resolutions — after all you can't really trade for or with it, no human player is interested in buying. And at the end of the day resolutions just don't matter that much to you individually outside of the diplomatic victory point, because they are inherently global. The slight edge that you might get from winning a resolution may positively impact a bunch of other people, and is rarely worth the production to get the favor necessary to win outright. So unless you're sure you can win Diplo, wonders like Statue of Liberty or Országház, or investments in a diplomatic quarter, may be mostly wasted.
This unfortunately means that Diplo needs to be a bit of a backup plan
Stopping Diplo: just, like, notice it's happening
The best way to stop a Diplo win is basic map awareness and coordination. Once someone has 12 Diplo victory points, you should be on high alert for the Statue of Liberty. Look for harbors that may not make sense otherwise, make sure you have at least passive visibility over folks with a lot of Diplo favor, and try and get everyone on the same page to oppose the person with the most diplomatic victory points.
It's really not hard! Part of the reason Diplo victories are rare is because they are fairly easy to stop, just vote against the guy who's winning! But you have to notice that it's worthwhile to do that, and against a good player that's the majority of the battle.
The last thought I have here is that military incursions can be especially devastating against Diplo player. Starting around the industrial era, most production boosts happen because of factories and power plants — things that incur big climate favor penalties that a Diplo player may try to avoid. That means they're going to be handicapping their own engine, at least compared to everyone else. And in some sense, you don't have to go after a Diplo player at all — simply take over any city states they may control.4
Concluding Thoughts
Diplomacy is a bit of a ‘tacked on’ mechanic in Civilization 6. It didn’t even exist as a win condition in the first release of the game. As a result, diplomatic favor and diplomatic resolutions both feel like they could be more impactful than they are. That has pros and cons. On the upside, you can kinda play a diplo victory without deviating too far from your base game plan. On the downside, investing heavily in diplomacy isn’t going to have meaningful returns. Still, it does feel pretty good to pull off a diplo victory — if only because of how frustrated it makes everyone else.
In the very late game, you can pick up Seasteads (future era tech) or Global Warming Mitigation (future era civic) for +1 point each. These almost never matter. If you have enough science/culture to get one of these, you almost always have a better shot just getting the science/culture win. That said, if you somehow have enough other Diplo points and you're finding it tough to pull off the win, switching to Diplo at the very end can work.
Though it's not always that bad — as you get closer to the end of the game, other civs will be eating favor penalties from excess pollution or from war mongering.
This is much easier to do if you have AI players in the game, who will generally vote for the same things across games.
You do have to make sure you aren't accidentally allied when the time comes to attack. I've lost at least one game by being unable to go to war with someone who was about to win due to an alliance.