Why don’t the Lannisters use their money as more of strategic advantage during the war of five kings? They hire Tyroshi sellswords and Vargo Hoat, so clearly they’re not opposed to using mercenaries. Nor is there a “code” against it in Westeros – Stannis hires Sallador Saan, and in TWOW he wants to hire the Golden Company. You’d think given his money Tywin would hire 10 or 20k sellswords and use them to fight Robb Stark. But we never hear about the Lannisters approaching the Golden Company etc.

They certainly did, but there’s a couple factors that prevented them from making full use of those resources in the phase of the War of Five Kings from the outbreak through to Blackwater:

  1. They’re on the wrong side of the continent, and Stannis and his navy stands between them and the Narrow Sea. So getting mercenaries to their army, and for that matter getting envoys to the Free Cities, would be rather difficult. 
  2. Stannis is competing with them for mercenaries. He’s hired around 3,000 already. And mercenaries are not a fully fungible product – mercenaries might be already under contract (the Golden Company was under contract with Myr, and given the then-impending war between Tyrosh and Lys, it’s quite likely a lot of companies had already taken up contracts with them), or be in some other region of Essos where it’s harder to contact them. As the WOIAF says, “when not employed by the three quarrelsome daughters, the sellswords oft seek to carve out conquests of their own.”
  3. The Golden Company is not really a possibility. Ser Jason Lannister died in the War of Ninepenny Kings, and Tywin, Kevan, and Tygett all fought with distinction against the Golden Company. Moreover, the Reynes and Tarbecks both fought for the Black Dragon in the First Blackfyre Rebellion, although they seemed to have reconciled with the Targaryens by the time of the Peake Uprising. 
  4. There’s a timing issue. At the outset of the conflict, Tywin wants to mobilize before everyone else to stack the odds in his favor – the same way he did in the Rains. That means attacking ASAP rather than waiting for mercenaries to go all the way around Westeros to join up with his army.

And then in the second phase, Tywin’s got the Tyrells he can call on, and a rather negative experience with mercenaries maiming his son. 

The enmity between the Reach marcher lords and the Dornish (e.g. Oakheart and Darkstar) seems unusually fierce given that they’ve been at peace for over 100 years. Do you think there’s been border raids etc over that time (and wouldn’t that be illegal/treasonous?) or is it just another example of long Westerosi memories and stasis?

There have absolutely been border raids: “the castles of the Dornish Marches are among the strongest of the realm, and for good reason, for seldom has a generation passed when hey have not faced some new attack…even during times of peace, raiders out of Dorne continued to descend from the Red Mountains in search of plunder.” But I’m highly amused at the idea that 100 years of peace means that enmity is unusual. 

We’re talking an enmity built over thousands of years of conflict. The very identity of the marcher lords of the Reach and the Stormlands is built on defending their land from (mostly Dornish) border raiders – you think the Carons forget that the Fowlers burnt their castle in 9AC? You think the Hightowers forget the Daynes burning everything outside the walls of Oldtown twice? Going further back, you think anyone in the Reach would forget that the Dornish sacked Highgarden, burnt the Oakenseat, and murdered Garth X in his bed? Over in the Stormlands, the castle of House Swann is built practically on the spot where the Yronwoods and Wyls were stopped in a battle so bloody it dammed the river Slayne. 

Also…100 years of peace is a bit of an exaggeration. Less than 10 years after Dorne entered the realm, you had the Blackfyre Rebellion (which as my forthcoming Tower of the Hand essay will point out, largely focused around Dorne), which Dorne fought in for at least three of the conflicts. Maekar died fighting in a rebellion on the Dornish Marches in 233. 

If you were a peasant (but not a slave), where would you *least* like to live? Lhazar, where you risk having the Dothraki kill you or sell you into slavery in Slaver’s bay? Naath, where the same thing might happen (except replace “Dothraki” with pirates)? Bolton lands? The Iron Islands? Sothyrous?

Urg, talk about a no-win scenario. 

In Westeros: Iron Islands is worst due to thralldom, but the Boltons come close, likewise most of the houses to have ruled Harrenhal. I can’t imagine it would be great to be smallfolk on the lands of House Clegane or House Wyl either.

In Essos: life among the Lhazarene seems rather precarious certainly. Naath seems like a paradise whenever the pirates aren’t there. Sothoryos I think the key thing is how adapted you are to the murderous flora and fauna. The Basilisk Isles seem awful. Nefer seems a bad place. As not the strongest dude out there, the three daughters of Hyrkoon would suck. Carcosa, K’dath, etc.