Most important, there would be nothing in such a picture of miasma, or of mud. There would be no mud-covered carrion, or living men covered in mud. Above all, there would be no women slathered with the stuff, or even women who, like Eliza, remained amazingly mud-free.

In fact, the fort at Humaitá was crawling with women. They detached themselves from the mud of the walls to approach in their mud-coloured dresses, and they opened their mud-coloured faces to show the wonderful, clean, inner red of their mouths, livid with teeth of yellow. And whatever they had to say, it was always a bother – a plea of some sort, for news of some man, for intercession over a scrap of cloth, or a scrap of roof to put over their heads, or, later, for food. They offered nothing in return, some of them, except the sight of their winning, female faces, or the prospect of leaving your sleeve alone. They might, either, offer some sexual service of great frankness, but their bargaining powers were in general poor, and they might switch from nothing to everything without seeming to tell between the two.

In the universal muddiness that pertained after that first action at Riachuelo (no one dared to call it a defeat), the merest wipe of a rag was enough to make you advance. The woman who fared best – at least the one whose sleeve Stewart would end up tugging before the war was out -started out with a clean face and a stand of rushes she cut from the swamp to repair your roof. She ended up supplying all kinds of things, from a bottle of French wine to woven baskets for the wall of the fort. She could be seen tramping them like a dumpy skirted engineer in increasingly good boots, with gold chains around her neck and other, dangling things hidden under the cloth of her shirt.

She was never hit. When the water rose, the Brazilian boats drew closer and the thick cushions of earth that were the walls became fatter and dangerously low, like hills. It was hard to tell if they were falling under the pounding or reverting to some more natural state and Stewart could not help feeling that they were quite happy subsiding like that, back into the easeful flat, or slipping off into the river again, as mud. He could not help the feeling that even the earth was betraying them now.

Still, it was fun. Every morning, they cheered a little paddle wheeler that steamed down to lob a few twelve pounders into the Brazilian fleet, making them scurry a bit, whip up a bit of foam. When it was sunk they sent Jaime Corbalan down instead – one man in a canoe full of torpedoes, with a ribbon presented by Eliza fluttering at his throat.

'We'll put a hole in them yet,' said Lopez as they waited for dawn and the sound of the first explosion, the plump ball of water bursting in the air. But there was nothing. There was an uneasy silence, which filled up slowly with the different kinds of misadventure and funk and betrayal, so by the time the first jeering whistle broke, they knew what had happened. The Brazilians had swallowed him up. Corbalan was a rich boy and this was the trouble, said Lopez, who, in his cheerful way, had the man's brother shot.

Then new boats appeared, and the shells flew high over the walls, churning an arc of mud where huts and shanties once stood. Every morning, the women went out to collect the unexploded canisters, then brought them to the gunners to be better primed and shot back. They cheered as they ran towards them, and jostled each other out of the way to keep their courage up, because although the shells looked like nothing at all lying there – just lumps of metal lodged in the muck – sometimes one would, under a woman's gentle touch, revive, and so explode.

Stewart faced the problem of the women whenever their anatomy ambushed him in the operating hut – every time he panicked that a man's member had been blown away and grubbed through blood and hair looking for the nonexistent wound. Every time he unbuttoned a shirt and found a breast, or two, beneath, he would sigh at the problem of the women. If Venancia were here, would she scavenge for shot? (Venancia becoming, as the weeks and months went by, as beautiful in his head as a glass of water, a plate of fresh food.)

Why, he asked himself, did the women do such a thing? There was a pot of corn for each shell, but there were other ways and other places where a woman might find food. Ί had a man who died,' said one, 'and then I had another man who died.' When life was so cheap, she seemed to say, love became general. So they might do it for a general love. Or for love of the General – Lopez. Or because they were told to – as simple as that; the love of discipline. Or because they loved the risk, as some of them undoubtedly seemed to do. They might do it, finally, because no one likes to lose -which is nothing but the love of victory, with her laurels and her wings.

Stewart was much exercised, philosophically, in his cholera tent and in his typhoid tent, by the problem of love. He thought about it obsessively. Perhaps it had always been thus, he thought, as he lifted a mustard plaster from a cholera victim's chest, or paused to examine the gassy, bulging ground over the pits where they buried the dead. 'My aunt always said I was a worrier.'

'But all love is a worried love,' he said, inadvertently aloud, and more than once. 'All love is fuss.'

He thought that he was beginning to love Eliza Lynch, for example. But properly, this time. This did not bother him much: it was a spiritual, even androgyne love – it was not a yearning thing. He did not wait for her to appear. But when she did walk out – her dress bouncing on its hoops, just clear of the mud, and her parasol glowing like a living membrane in the sun – her eyes were so kind, her whole air so simple and redeeming, that it was impossible to call her a woman at all. She was like a sister when she moved and like a dream when she was still. She was what they were all fighting for.

Of course, he was also in love with her in a dashing sort of way – they all were, it was the accepted thing to be. 'We have died and gone to Eliza's', was the joking toast they gave, in the little place she kept beyond the church at Humaitá – meaning no disrespect in this use of her Christian name, but on the contrary, a kind of bantering beatification.

Eliza's house was a haven – partly because it was so well back from the arc of bloody muck that was the ballistic limit of the Brazilian ships. Which is not to say that Eliza was a coward; she walked freely out; a distinctive sight -you might even say a target – a swirl of colour with two boys, fore and aft, to lift and lay boards for her feet. They got so adept, it became a kind of game with them all; Eliza walking faster and faster as they ran around her, forming an impromtu wheel on whose inside rim she walked safe.

Stewart could have used the boys, but he did not grudge her this courtesy. It lifted all their hearts to see her looking so fine. There was not a man among them, would not lay down his life to save her stockings from a splash of whatever liquid might taint her: muck, blood (sperm, he idly thought), pus, noble or otherwise, and, God knows, sweat; the soup of putrefaction; good, old-fashioned shit -there being so many ways in which a lady's stocking might get wet, these days.

Every time Stewart saw Eliza, she had grown. He was not surprised by this; Venancia had, for example, shrunk in his head, until she had become a sort of daughter to him – a body he might take up in his arms, fresh and light and loose as water. And sometimes the body was alive and sometimes the body was dead. Either way, even though Stewart knew she was eating her way through her father's estate upriver, along with his own worthless salary, she still became, as the months and years went by, lighter and lighter in his mournful arms.

He himself, he thought, was pretty much the same size, although he could feel his heart getting bigger. His heart seemed to be, by now, the size of a horse's heart, and as the pile of food shrank and the pile of bodies grew, it felt like his heart would take over the entire cavity of his chest, until he was just a thumping, possibly empty, thing of muscle and bone.