Game of Thrones’ seventh season, one defined by the show’s most central characters all coming into conflict for the first time, is over. Daenerys, Jon, Cersei, Tyrion, Sansa, and all the rest spent the entire season struggling with one another for power and control over Westeros, each employing different strategies to strengthen their faction and accomplish their objectives.

Which makes the season’s end a perfect time to take stock: to assess each player’s strategy, and judge which character did the best with the tools they had available. Who played the Game of Thrones best?

To make this judgment, I looked to science — political science, specifically. The subfield of international relations has spent decades accumulating knowledge on what causes different countries to rise and fall, to succeed at getting what they want or to fail miserably. A lot of this work applies just as well to Westeros, with a little bit of tweaking, as it does to Earth.

So as the season ended, I sat down and thought about which characters were most successful and why. I also consulted with a bona fide expert — Dan Drezner, author of Theories of International Politics and Zombies and a professor of international relations at Tufts University’s Fletcher School — to help figure out how political science helped explain who won and who lost on Game of Thrones this season.

What follows, then, is a definitive ranking of whose strategies were best in season seven, from worst to best, focusing only on players who had a major role in the global conflict this season (sorry, Bran, Sam, and Jaime).

So here’s the ranking. And remember, you can’t argue with it — it’s science.

12) Daenerys Targaryen

At the beginning of the season, Daenerys had every piece in place to succeed. She had the world’s most powerful army, three strong allies, a compelling objective of “breaking” the wheel that had hurt ordinary people, and — most importantly — she was the sole possessor of the world’s most powerful military technology, dragons. By all rights, she should have ended this season atop the Iron Throne and ready to confront the White Walker threat in the North.

She failed, miserably.

Daenerys lost two of her three allies — Dorne and Highgarden — and the leader of her third, Yara Greyjoy, was captured. She gained a new ally, Jon Snow, but he didn’t make up for the losses. And she idiotically delivered a dragon right into the hands of the Night King, her most serious rival for military hegemony. Her incompetent strategy literally endangered the entire planet, and for that she deserves the lowest spot in this ranking.

Why did Dany fail so epically? Her nation was what’s called a “revisionist” power in international relations parlance, meaning a country that is attempting to upend the political status quo and create a new international order whose terms they dictate. Think Napoleon’s France, World War II-era Japan, or modern-day Russia.

In a statistical study of revisionist powers, Yale University’s Jason Lyall found that revisionist powers often fail by adopting disastrous strategies. They do so, Lyall argues, because leaders build support by winning a military victory of a certain kind. These leaders make grandiose promises of a new world, and need to show that they are delivering. As a result, they build strategy around fulfilling their promises, and often adopt risky approaches that seem appealing, rather than smarter ones that less obviously fit they way they sold themselves.

This is the precise issue that affected Daenerys this season. Early on, she pledged to be a benevolent conqueror, not to burn King’s Landing to the ground or occupy cities with foreign troops. This led her to keep her dragons at home entirely, rather than think more creatively about using them. Why not burn the Red Keep and kill Cersei — but leave the civilian centers of King’s Landing alone? Why not send the dragons to burn Euron’s navy? Why not use the Dothraki cavalry to harry Cersei’s military, staying out of sight of King’s Landing but ambushing any Lannister forces that dared leave the capital?

Later in the season, after losing most of her main allies, she became obsessed with winning Jon’s loyalty — leading to the precise opposite problem. She put her dragons at too much risk, sending them to rescue Jon in a situation where the enemy’s military capability was not well known. She managed to save Jon and win his loyalty, just as Lyall’s theory would predict — but also handed a weapon of mass destruction to a power bent on literally extinguishing all human life.

This was revisionism at its most incompetent.

11) Petyr “Littlefinger” Baelish

Littlefinger, of course, is dead. All of his scheming amounted to nothing in the end, his throat cut at Arya Stark’s hand while the Knights of the Vale — ostensibly his soldiers — sat and watched. His failure is second to Daenerys’s only because he had a lot less to work with, and the consequences mostly rebound on him rather than the entire world.

The issue here was overreach. Littlefinger wanted to marry Sansa and secure his claim to the North, but felt he couldn’t do that while Arya — who didn’t trust him — was around. So he plotted to turn Sansa against Arya, which led the two of them to instead decide to eliminate him. With no truly loyal allies, Littlefinger was defenseless when the Lady of Winterfell turned on him.

This is a problem with Littlefinger’s entire approach to gaining power. He believed the only thing that mattered was the power of the forces you command. But Westeros is a society defined not only by pure power politics, but rather by a series of ethical beliefs and rules of etiquette. There’s an entire school of international relations theory, called constructivism, devoted to explaining the importance of these ideas — and scholars think it applies fairly well to Westeros.

“Social relations in Westeros are sustained as much through bread-breaking rituals, arranged marriages, and promise-keeping as through backstabbing and treachery,” Charli Carpenter, a professor of international relations at the University of Massachusetts Amherst, writes at Foreign Affairs. “The power of such rules is only highlighted by their occasional breach.”

The first of these rules among the Westerosi nobility is loyalty to family. The Starks, a family famous for their commitment to ethical rules, would never turn on each other. Littlefinger did not understand the nature of this belief, and believed he could turn Sansa to his way of thinking. By overestimating the power of fear and power lust, and underestimating the force of Westeros’s moral rules, Littlefinger sealed his fate.

10–8) Olenna Tyrell, Ellaria Sand, and the Greyjoy siblings [TIED]

Daenerys’s initial three allies all kicked off season seven as leading members of the world’s most powerful alliance — and ended in disaster. Olenna is dead. Ellaria was forced to watch her daughter die in front of her eyes. And Yara Greyjoy is a prisoner of her uncle Euron, with her brother Theon is on a dangerous mission to rescue her.

What happened here was very simple. These leaders all attempted a strategy called “bandwagoning” — aligning yourself with a stronger power. Ohio State University’s Randall Schweller argues that countries tend to bandwagon with revisionist powers like the Targaryen alliance when they want to strengthen their position in the international system.

This all made sense at the beginning: Cersei murdered Olenna’s family and destroyed their chance to take over the throne, Ellaria hated the Lannisters, and Yara/Theon needed someone’s help in overthrowing Euron.

But the problem with bandwagoning is that your fortune rises and falls with those of the great power you’ve aligned with. When Daenerys proved too timid and uncreative to win an early victory against Cersei, her allies were the first casualties. Daenerys’s allies overestimated her chances, and paid the price.

7) Tyrion Lannister

Tyrion’s situation was a little different from that of the other leaders we’ve talked about so far. His situation wasn’t just about developing a strategy to beat his sister — though he clearly didn’t perform very well on that front. It was, first and foremost, about maintaining his own position as Dany’s Hand and using it to steer her toward the right course of action.

He did all right: He still had his job by the end of the season, and Daenerys clearly trusted him to lead the negotiations with Cersei. But at several times throughout the season, he managed to unnecessarily marginalize himself and weaken his influence with his queen. Tyrion consistently advised Daenerys against deploying her dragons, even after it became clear in the fourth episode that Daenerys wanted to do so. After the success of that episode’s raid on Jaime Lannister’s army, Tyrion had very little credibility to counsel against the dragon raid to rescue Jon, the season’s most epic disaster.

This is a point that Harvard’s Graham Allison emphasizes in his famous book on the 1962 Cuban Missile Crisis, The Essence of Decision. Allison argues that when leaders have decided on a course of action, they want their advisers’ approval rather than advice. Advisers who want influence over future decisions need to provide that approval, and try to shape the decision, rather than openly challenge their leader. Doing so will only marginalize them and lessen their influence.

By counseling against dragon raids all season long, Tyrion burned his own credibility on the subject of dragon raids. The reason he felt so ineffectual for much of the season — and indeed, moped about it on a few occasions — is that he did a bad job reading Daenerys’s opinions and maximizing his influence over her. He’s a very smart man, but he’s still learning how to handle his queen.

6) Arya Stark

Arya is the first character we’ve looked at who succeeded at her objectives more than she failed.

Her strategy throughout season seven was simple and consistent: kill her house’s enemies. She began the season by assassinating Walder Frey and all of his male heirs in retaliation for the Red Wedding, and ended it by executing Littlefinger for his (many) crimes against the Starks.

This actually worked out pretty well. The Freys seem to have been eliminated as a major force in Westerosi politics, and Littlefinger’s death actually seems to have solidified Stark control over the Knights of the Vale, a vital part of their military force.

This tracks with real-world statistical evidence that decapitation — meaning killing an opponent’s leader — can effectively weaken its entire force under certain circumstances. One such situation, Georgia Tech’s Jenna Jordan argues, is when the enemy has a “charismatic” leadership structure. This means that the enemy is held together by one or a handful of powerful leaders, and functions because of that person’s leadership rather than any kind of bureaucratic structure or ideological bonds.

This condition applies to both of the enemies Arya took on. House Frey was a family business, led by its men; killing the entire male line ended the threat. Littlefinger held his forces together through sheer force of will; when he was exposed and eliminated, there was no organization that would continue his shadow campaign to undermine Arya in his wake. Arya chose the right targets and killed the right people.

5) Euron Greyjoy

Euron is a weird one, since his most important move — building up a massive fleet after Yara and Theon stole the core of the Greyjoy navy — happened offscreen. But it’s hard to deny that he played his poor hand brilliantly: He started out the season a weak ruler of a divided island kingdom, and ended it with a real shot at becoming the king of Westeros via a promised marriage to Cersei.

The key move here was leveraging industrial capacity (the ability to build up such a large navy so quickly) to make smart moves in power politics. Euron identified that Pyke had a resource that a powerful player needed — a fleet — and provided that capacity in exchange for promises of a permanent alliance.

This calls to mind the rise of the US as a global power. As Fareed Zakaria documents in his book From Wealth to Power, the United States had the economic capacity to play a major role in global politics — to build up a powerful military and wield major diplomatic influence — far before it actually did so. What it took, Zakaria argued, was a concentration of power in the executive branch, and presidents willing to use that power to exercise influence abroad. This happened in the late 19th and early 20th centuries, starting (more or less) with the Spanish-American War.

That’s exactly what Euron did for Pyke. Think of him as the Iron Islands’ Teddy Roosevelt, a swashbuckler who became his country’s leader and helped shape it into one of the world’s great powers.

4) Sansa Stark

Sansa had a lot of responsibility this season. She had to maintain the North’s loyalty as Jon was off trying to negotiate with Daenerys, while simultaneously fending off Littlefinger’s scheming. She succeeded brilliantly at both.

Sansa was perhaps the only character who spent time onscreen preparing for the long upcoming winter, managing problems like how people would feed themselves when crops might not grow for years. Her effective stewardship won her the loyalty of the Stark bannermen — an impressive feat for a young woman in a patriarchal society.

Playing off gendered expectations, actually, was vital to her success in the struggle against Lord Baelish. Feminist international relations scholars, like Clark University’s Cynthia Enloe, argue that the international system functions on the invisible, less prestigious work often assigned to women. This is even more true in Westeros, a place where men literally inherit power and alliances are formed through marriage, than it is on modern Earth.

Sansa understood this gendered system, and how it shapes everyone’s expectations, better than anyone. She repeatedly said that she knew what Littlefinger wanted — her body and her hand in marriage — and she was right. She played off Littlefinger’s expectations, letting him believe that she might actually consider allying with him, lulling him into a false sense of security while she quietly schemed against him. By playing off the male belief that a man’s pathway to power was through controlling women, she out-manipulated the show’s most effective manipulator.

That she did it in conjunction with her sister, in defiance of the catfighting trope that Game of Thrones appeared to be setting up, was the cherry on top.

3) Jon Snow

I’ve argued before that the best way to think about the White Walkers, from the human point of view, is as a threat akin to climate change — a massive collective threat that humans were ignoring in favor of petty internal squabbling. Jon, to his immense credit, is the only leader who recognized the enormity of the threat early enough to try to rally others to stop it. He’s kind of a Westerosi Al Gore, only he succeeded in getting to run a country.

So the best way to think about Jon’s mission is through the lens of environmental diplomacy: He needed to convince the world’s leading powers to abandon the internecine struggle over the throne and refocus on the White Walker threat. He didn’t have a ton to work with: The North is a distinctly third-tier power, weaker militarily than both the Targaryen and Lannister alliances and the country most vulnerable to the White Walkers.

Jon may have failed to rally Cersei to his cause, but he succeeded in bringing on Daenerys. And that’s by far the most important, mostly because her dragons and cache of dragonglass represent the only chance humanity has at fending off the White Walker threat. If it weren’t for Jon, humanity would be fundamentally doomed.

The London School of Economics’ Robert Falkner argues that in our world, global environmental agreements only succeed when they have some American buy-in. Because the United States is so dominant in the international realm, controlling so much of the world’s resources, it effectively has veto power over whether an agreement can work.

Daenerys is the American equivalent here, and Jon convinced her to commit 100 percent to the battle in the North. He actually went further than that: By getting Dany to fall for him, he raised the possibility of marriage. Icky incest aside, this gives the North a chance to sit one of its own on the Iron Throne for the first time in Westerosi history. Jon not only built a dominant anti-White Walker coalition but laid the groundwork for a permanent alliance with Westeros’s greatest power.

2) The Night King

All of the White Walkers’ seemingly aimless wandering paid off the moment undead Viserion punched a hole in the Wall itself. Now the Night King’s forces are streaming into Westeros proper, where they have access to huge human population centers that they can kill and then raise as wights. The army of the dead is the scariest it’s ever been.

This is all thanks to the Night King’s patient strategy.

The conflict in the North was defined by what scholars call the offense/defense balance. The term, coined by Columbia University’s Robert Jervis, refers to the idea that technology can fundamentally shape whether states are likely to go to war. The Wall was a dominant defensive technology — it made it difficult, if not impossible, for the White Walkers to actually mount a successful assault on the Seven Kingdoms. The Night King correctly identified this challenge, and focused his energies on killing humans and giants and bears north of the Wall that could then be raised to make his army stronger. In essence, he engaged in a massive military buildup while waiting for a time when technological developments would shift the offense/defense balance.

And it did, the minute Daenerys sent dragons into his grasp. When the Night King killed Viserion and took control of him, he gained control of a technology that trumped the human’s chief defensive technology. He then attacked essentially immediately, busting through the Wall and into the North while the bulk of the human forces were deployed down south.

With undead Viserion in his grasp, the Night King is arguably the most powerful military force in Westeros. And he’s in a prime position to make his army stronger by sweeping across the North.

1) Cersei Lannister

Who else could it be?

At the beginning of the season, Cersei was isolated and friendless. She was surrounded by enemies, her kingdom was deeply in debt to the Iron Bank, and she was facing a kind of military threat — dragons — that she simply had no answer to. It seemed like most people, as my colleague Andrew Prokop writes, expected her to die this season.

She didn’t — and, in fact, she ended up in a position where she could plausibly win a war that once seemed impossible. She had neutralized a number of opponents, recruited Euron and the all-powerful Iron Bank to her side, used the Iron Bank to finance the purchase of a powerful mercenary force, and pitted her two most dangerous enemies (Daenerys and the Night King) against each other.

To understand Cersei’s success, we need to reach back to the classic work of Prussian military theorist Carl von Clausewitz.

Clausewitz is most famous for his book On War, specifically the phrase “war is simply a continuation of politics with other means.” This is a commonly (mis)quoted phrase, but its meaning is actually quite subtle. Clausewitz is arguing that war is one tool of statecraft and nothing more. The goal of fighting is the same as the goal of economic sanctions or diplomatic negotiations: to accomplish a desired political end. Just because it’s bloodier doesn’t make it fundamentally different.

Cersei, to her credit, internalized this lesson more than anyone else. She dedicated herself to one objective — protecting the survival of the Lannister dynasty and the life of her unborn child — and centered every tool of statecraft on accomplishing that goal.

She pledged to marry an unpleasant pirate, exposed a large chunk of her army to dragon fire in the name of acquiring vital gold to pay back the Iron Bank, and even let her ancestral home of Casterly Rock fall to put her enemy in a strategically vulnerable situation. No other Westerosi power thought as creatively about how to link the major aspects of state power — military, economic, and diplomatic — in order to accomplish a particular political end.

My guess is that Cersei’s approach will all come crashing down on her head next season, owing to her alienation of her brother and paranoid, backstabby ways. But that’s a guess. Just looking at the arc of season seven, it’s clear that no one played the Game of Thrones better than Cersei Lannister.

Correction: An earlier version of this piece said that Jenna Jordan is on the faculty at the University of Georgia. She in fact is at the Georgia Institute of Technology (Georgia Tech).