What exactly is the geopolitical significance of the Three Sisters?It can’t be fishing rights, the Manderlys are doing fine in that regard while the Sistermen are better known for their shipwrecking. I also don’t remember reading about any attempted invasions by the Vale using the Sisters as a springboard. So why the 1000 year war?

It’s much more about naval control over the Bite than fishing rihgts, and the Worthless War came about in the wake of a series of naval conflicts between the North and the inhabitants of the Three Sisters:

“Even before the coming of the Andals, the Wolf’s Den had been raised by King Jon Stark, built to defend the mouth of the White Knife against raiders and slavers from across the narrow sea…During the wars between Winterfell and the Andal Kings of Mountain and Vale, the Old Falcon, Osgood Arryn, laid siege to the Wolf’s Den. His son, King Oswin the Talon, captured it and put it to the torch. Later, it fell under attack from the pirate lords of the Three Sisters and slavers out of the Stepstones. It was not until some thousand years before the Conquest, when the fugitive Manderlys came to the North and swore their oaths at the Wolf’s Den, that the problem of the defense of the White Knife—the river that provides access into the very heart of the North—was resolved with the creation of White Harbor.

…The last isles to be wedded to the Vale were the Three Sisters. For thousands of years, these islands had boasted their own cruel kings, pirates and raiders whose longships sailed the Bite, the narrow sea, and even the Shivering Sea with impunity, plundering and reaving as they would and returning to the Sisters laden with gold and slaves. These depredations finally led the Kings of Winter to send their own war fleets to seek dominion over the Sisters—for whoever holds the Three Sisters holds the Bite.”

So it’s absolutely the case that the Three SIsters *used* to be pirates and slavers, and shifted to becoming wreckers when more powerful forces cracked down on them, although they clearly still do a bit of piracy, because Stannis hanged twelve Sistermen for piracy when he was Master of Ships. 

As for attempted invasions, well, where do you think Osgood and Oswin Arryn based and resupplied their ships from when they attacked the Wolf’s Den?

Is Myranda Royce snobbish about the Sistermen in TWOW because they’re poor, or because they’re not integrated into the Vale political polity, or some other reason?

Good question! 

I think there are a couple different factors going on:

The Sistermen are not part of the mainland but rather out on the extreme periphery of the Vale:

  • Because the Sisters became part of the Vale after the Battle of Seven Stars, they don’t have the cachet of having fought for the Andals and the True Religion (in the same way that a certain kind of WASP looks down on people who didn’t come over on the Mayflower or whose ancestors didn’t fight in the American Revolution) and are instead provincials.
  • Because they live far off, they’re not a regular part of court life, and although definitely the highborn families would be treated as highborn, they certainly wouldn’t have the cachet of the inhabitants of the Vale proper.
  • Because they don’t live on the mainland, they don’t share mainlander concerns about mountain clans raiding or growing seasons or mountain passes being closed off by snow, etc. 

The Sistermen are moreover a historically rebellious and quasi-criminal part of the periphery. 

  • Before the Andals came, the Sistermen were pirates and slavers, neither activity likely to make them popular with the people they steal from or the people they steal. And to the present day, a big part of their economy is smuggling, and wrecking – the mainlanders despise honest merchants, so these guys are going to be seen as the lowest of the low.
  • As the mainlanders see it, the Sistermen started the Worthless War by being greedy pirates who poked the wolf one too many times, and not a small part of the mainland suffered as a consequence.
  • Then after the Arryns rescued the Sistermen, they rebelled against them during Aegon’s Conquest, and then against them and the Targaryens during the Blackfyre Rebellions. 

And finally, there’s the whole inbreeding/webbed fingers and toes thing, which probably means they’ve interbred with the Squishers…