Edmure Tully should have talked back to the King in the North.

On last night's Game of Thrones, the new character of Lord Edmure (Tobias Menzies) can't understand why his nephew and king, Robb Stark (Richard Madden), upbraids him for beating the hated Lannisters. Robb explains that Edmure made a dumb battlefield decision – more on that in a second – that redounded to the Lannister enemy's benefit, all for negligible strategic gain. It's never wise to talk back to the King, but someone needs to tell Robb: Oh, you mean like your entire war plan?

Not only is Robb Stark the white hat of Game of Thrones – a warm, generous and reluctant king – he's portrayed to viewers as one of its fiercest warriors. "He's a boy, and he's never lost a battle!" rages his enemy, Tywin Lannister. But the Young Wolf is a case study in the difference between winning battles and winning wars. Robb is an excellent company commander, leading from the front and inspiring his men with both his bravery and his battle prowess. He's also a terrible general.

Robb's bad decisions as a king are shaping up to be a major plot point of the third season of Game of Thrones, much as they are in its source material, George R.R. Martin's A Storm of Swords. But the HBO series, which has the unenviable task of adapting a sprawling storyline for TV, obscures Robb's equally poor generalship in an understandable search for narrative economy. You can still see why the Young Wolf needs to rescue his war from himself this season, but the show doesn't make it easy.

For instance: the gorgeously rendered map displayed during the opening credits never shows you the Westerlands, an omission with inadvertent implications. South of the Iron Islands and just beyond the Riverlands, the Westerlands are the heart of Lannister territory, the source of House Lannister's immense wealth – and the field of battle for Robb's campaign. You can be forgiven for watching all the beautiful scenes with Robb and Lady Talisa in the second season of Game of Thrones and not having a clue where any of it takes place. (Tywin fuming that Robb is "too close to Casterly Rock!" is about as much as the show provides.) Without a sense of the terrain, you can't really understand Robb's war. So to make all this clear, we've mapped Robb Stark's march from Winterfell, through to last night's episode.

Robb Stark's march from Winterfell, through the Westerlands, and ultimately to Riverrun. Map: Simon Lutrin/Wired.com

You don't have to be a West Point grad to see the problem here.

Robb launches his western expedition at the beginning of season two. He has fewer soldiers than the Lannisters, and no seapower. Instead of marching on King's Landing, Robb's plan is to attack the Lannisters' home turf until they sue for peace – and acknowledge northern independence – and his means is to "litter the south with Lannister dead." Robb defeats Stafford Lannister's army at Oxcross, the offense for which King Joffrey has Robb's sister Sansa stripped and beaten in King's Landing. Then he pushes to the western coast, at the Crag, to accept the surrender of its lord and Tywin's bannerman. So far, so good.

But at the beginning of season three, Robb marches his army way eastward to Harrenhal – something that isn't in the books – where Tywin ordered his brutal lieutenant Gregor "The Mountain" Clegane to command a garrison force. It's an inexplicable decision (one concealed, alas, by the show's poorly explained geography of the west): Robb has given up raiding the heart of Lannister country to cross over into the Riverlands, all to defeat one admittedly mountainous henchman. The Lannisters "have been running from us since Oxcross," Robb notes, even though the northern army is outnumbered. Robb might have thought harder about why that is.

By ceding the west, Robb does Lord Tywin a massive favor. Tywin faced a difficult decision at the end of season two: march west to fight Robb and risk Stannis Baratheon seizing the capitol at the Battle of Blackwater Bay, or march to King's Landing and risk Robb laying waste to the Lannister stronghold. Once Robb leaves the west, the Lannisters face no pressure at all. Suddenly, Robb is caught between the remnants of the Lannister field army to his west and the Lannister/Tyrell alliance at King's Landing. Whatever battlefield successes he gained on the Lannisters' ancestral doorsteps grow more ephemeral every day.

And for what? First Robb arrives late to Harrenhal, unable to do anything but mourn 200 dead northern soldiers, presumably slaughtered by Clegane, who's long gone. (Apparently Clegane killed an advance raiding party.) Then, when given word of his grandfather's death, he takes his army and marches it back somewhat westward, to Riverrun, to attend the funeral. "This march is a distraction," the aggrieved Lord Rickard Karstark tells Robb. Robb churlishly accuses Karstark of losing faith in the northern cause, but Karstark is merely pointing out the obvious.

Then there's Edmure. Robb's vainglorious uncle clearly messed up by disobeying orders to hold Riverrun, preferring instead to stop Clegane's army at Stone Mill from crossing the rivers of the Trident and heading west. Robb rolls his eyes: he wanted Clegane to come west, so the Mountain, who "doesn't have a strategic thought in his head," would have been lured unsuspecting toward the eastward-marching Stark forces and killed. "Instead," the King in the North laments, "I have a mill."

News flash, Your Grace: Clegane is not worth much more than that mill. If Robb managed to kill Clegane, Lord Tywin would still have the combined strength of Highgarden and the residual Lannister power at King's Landing. Sansa will still be a hostage. Joffrey will still be in power. The north will still be under threat from both the Lannisters and the invading Ironborn. Robb will have Clegane's very large head. That's the thinking of a company commander, not a general. Edmure can't be blamed for following his commanding officer's example.

This all makes more sense in the books – but not much more.

In George R.R. Martin's version, Robb initially heads to Riverrun after crossing the Twins, to break the Lannister siege of his grandfather's castle. Robb orders bannerman Roose Bolton to march east to Harrenhal and take it from the Lannisters, while he marches west to lay waste to the Westerlands, moving from Oxcross to Ashemark and finally to take the Crag. There, Robb suffers an arrow in the arm and gets, er, comforted by Lady Jeyne Westerling, so much so that the honorable Robb marries her. (By substituting the invented character of Lady Talisa for Jeyne, the show misses an opportunity to clarify the war in the West from the perspective of a stakeholder.) Then he marches back to Riverrun for the funeral, upbraiding his uncle Edmure for the debacle at Stone Mill – which really is a debacle in the books, because the impetuous Edmure blocked Tywin Lannister's move westward, not just Gregor Clegane's.

Tywin was trying to get west to stop Robb and break the northern pillage of his lands. That would have given Robb a chance to ambush Tywin, kill or capture him, and drive the Lannisters into disarray right as Stannis was about to arrive at King's Landing. But when Edmure throws Tywin back across the Trident, Tywin has an opportunity to march southeast, link up with the Tyrells, and repel Stannis' invasion. Oh, and Edmure also dissolves his army after Stone Mill. Nice going, Lord Tully.

Still, even in A Storm of Swords, Robb is hitching his hope for the war on a masterstroke, which is terrible wartime leadership. He'll win – if Tywin pursues him west; if the ensuing battle breaks his way; if Stannis wins at the Blackwater. And marching east to Riverrun for Lord Hoster's funeral in the aftermath of that plan failing amounts to Robb abruptly ending his own assault on the west before forcing the Lannisters to feel any real pain. It's a shame to lose a grandparent. It's much worse to risk losing a war.

So, at this point in the show, King in the North has two martial options available. One is to push back into the west, lay siege to Casterly Rock and Lannisport with the additional strength of Riverrun, bleed the west and force the Lannister/Highgarden alliance into open conflict. That's a last-gasp plan – the North and the Riverlands may not have the manpower; and if Robb loses, he dies – but it has the benefit of taking the west away from Tywin, Joffrey and Cersei.

The smarter plan is to retreat to the North, root out the Ironborn invaders, and reiterate the North's declaration of independence. Yes, that has the drawback of leaving Sansa in Joffrey's grasp. But Robb needs to think like a general. He has something Joffrey and Tywin want: the North. (That is, if he can win it back from the Greyjoys.) He needs to draw their armies north, onto his own territory, where northerners are better positioned to throw the Lannisters back and bleed them to death in a winter campaign that stretches the Lannister supply lines.

If Robb's goal really is to free the North from King's Landing and not merely to kill Joffrey, this is the way to do it. It'll probably involve crossing the Twins, and Walder Frey probably won't be happy about that after Robb insulted him by breaking a marriage contract with his family. But even Cersei tells Joffrey in season one that the North is "too big and too wild" to conquer. Robb needs to turn that to his advantage.

"I'm fighting a war," Robb tells Talisa in season two, "and I don't know whether I should march south or north." In the books, Robb puts it more bluntly. "I've made a botch of everything but the battles, haven't I?" he confesses to his mother. "I thought the battles would be the hard part, but..." Welcome to the first lesson of generalship, Young Wolf: you can win every battle and lose the war.