Out of the horizon the army comes on Remade horses, camels, steaming jitneys that grind on many wheels. They come in formation into the smokestone. The wyrmen of the iron council track them, flying higher than smokestone might set.

The graders blast the capricious geography. They watch anxious and inexpert for any sign that they have split a smokestone seam.

Other crews lay huge charges in holes they carefully dig, directed by the crawling geoempath. She licks the dirt with animal sounds, in some crude ecstatic trance. Hers is not a strong or focused talent, and trying for such powerful prehension of the earth debases her to it.

Iron Councillors build barricades in a yardang between set faces of cloud. A mile off are the smoke and downlaid and uptaken rails of the perpetual train. Uzman and Ann-Hari are on board, while Judah and Thick Shanks and hundreds of others are ambushers.

They can see the army now. Judah is drained after his preparations. He is already so tired that his dreams are slipping into his thoughts. He must return to iron council as soon as he can. It needs his protection. He has built a golem trap on the cowcatcher, has told them how to trip it should the silicate mist appear, but a golem of air will not last without his shepherding.

-There must be other attacks, he says, as they have all said. This cannot be the only front New Crobuzon will open. But there is no time to think of that now as the attackers come close enough, and before their first guns sound to destroy the ramparts, the iron council attacks.

The wyrmen hammer the air with their thick wings, wheel through shots and drop their clay grenades. Bullets snatch them out of the air.

Bomblets drop, made of whatever the council has: gunpowder, the shrapnel of torn-up tools, vials of crude acids, unpleasant thaumaturgic compounds, oil. Naphtha, caustics, hot smoke unfold and the militia break a little, but they re-form fast, break again at a second sortie of wyrmen. The sun is bright but seems suddenly very cold to Judah.

-It ain’t far, he is muttering. He hears himself. -Ain’t got to do this long.

He leans out, field glasses to his eyes. Wyrmen defecate their contempt on the enemy as they let their missiles go. One bursts: Avvatry, a truculent bull Judah knows enough to greet, taken apart with fusillade so he reaches the ground more rags than animal.

The Councillors fire arbalests made in iron council’s foundries. They light fuses and send rockfall down on the invaders. Judah knows this is his fight to win or to lose.

Judah stands. He stands on the rampart. Wires trail from him, to batteries, to a transformer. He trembles with bravery.