Once, west of the Caribbean.

He is a farmer and he loves his land... He has a patch, an area of cultivation on the side of a hill, and in the years since his father died he alone has made it bloom. In spring he aerates the soil, breaking through the laterite crust that built up in the previous year's sun. When the rains come he clears out the new silt that fills in the irrigation channels. This muck is thick, and he spreads it across the least forgiving parts of his fields to bring them the fertility that comes naturally elsewhere. The curvature of the hill is just enough that each year he has to pick through the soils and remove the rocks that rolled down from above, a soft limestone slab here or a hard granitic clast there. His wife is slowly building these into an oven, and given a few more years may be able to cook a better meal than the kitchen fire can provide. They may even persuade his cousins that the harvest festival should be here rather than at his uncle's house.

Last year the maize crop was rich, and this year there have been few clouds, plentiful rains and even the peppers are reaching towards the sky. He has high hopes that after tribute there may be enough left over to bed in comfortably over winter. Taxes are hard, but his family has always been able to pay and between him and the collector they both know how far it will go. He’s heard the discontented voices from the south, but suspects it’s just laziness that causes them to complain. He is richer than his parents, and his parents were richer than theirs. It was three years since his last child was born, and maybe this year his wife can bear another. An Aztec family should have sons and daughters.

The Spanish Are Coming

I had a nightmare last night.
The Spanish are coming, and there is nothing, nothing we can do to stop them.
They are building a colony, driving down their roots into an island just across the straits.
Soon they'll have a platform from which to explore, with support not weeks or months but merely days away.
They have cannons, they have horses and they are excited by adventure... All we have are feathers, rocks and organisation.
The Spanish are coming, and we haven't heard a call.

A pike is a wooden pole with a sharpened tip at the business end, typically running at three to seven meters in length. Up until the common use of rifles this was without doubt the best way to fight cavalry. The Aztecs have no concept of the the pike. There's a reason for that - between single combatants this is a ridiculously inefficient weapon, tempting the attacker to drop it and run at their opponent with open hands, or treat it as an unwieldy club. Scaling up, two united men with pikes are a potentially worrying oddity. But twenty united men with pikes make a hedgehog, capable of holding a line against anything but the best ranged weapons, and European warfare had developed this into a fine art. Ever since 331 BCE when Alexander the Great slaughtered Darius of Persia's chariots in the Battle of Gaugamela the pre-eminence of a long, spiked pole in a soldier's calloused hands was recognised. It would stay that way till well into the age of the musket. Driven into the dirt and pointing at chest height it gave fear to horsemen, and without it horsemen terrified the infantry. Battle had three components - ranged weapons, cavalry and infantry - and the balance between the three had been optimised over thousands of years. Thirty combatants with pikes might seem ridiculous and immobile when on the attack, but when steel tipped, hand finished and well braced these tools had turned many battles.

On the American landmass, there is no pike... The only domesticated mammals here are the Inca's llama and guinea pig. The locals had to build a society without that particular luxury. In the Old World domestication began in Turkey, which just happened to have fauna (horses, sheep, oxen) ideal for brutallising till it obeyed; and this practice had spread across the continents. Back in the New World, the only way to move something from point A to point B is to get someone to pick it up and carry it. Here, the wheel might be a clever invention, but its a lot less use without a horse to pull it along. In the Aztec empire the alternative is humans. And if you've got a lot of things you need to move, that means slaves. To build their civilisation they needed either a lot of slaves, or a way to extract labour from their defeated foes as tribute. Their neighbours didn't like that much, but really who cared what they thought? Aztecs rule through fear, or not at all.

The effect this has on warfare has been that while on occasion an opponent may represent an existential threat that must be wiped out at all costs, most of the time war awas aimed to take prisoners as slaves. They optimised their troops with this in mind. Thousands of men equipped with throwing spears, obsidian embedded wooden swords and archers - Aztec warfare was about mobile, lightly-armoured, troop rushes. These tools aren't really suited to a quick kill, so taking enemy prisoners rapidly from their front line looked like a promising tactic, but that needed organisation. Their wars were a game of tag played with obscenely high stakes. The new European colonies that had taken hold of Cuba had come with a very different concept of war.

How do you invent, build, train and optimise your troops for pike tactics in a matter of months?

Tenochtitlan, the Aztec capital, is bigger than almost every city in Europe. Only the recently annointed Turkish capital of Constantinople rivals it for size. A population of 300 000 in the middle of Lake Texcoco. Carefully town-planned, with roads, canals and wooden bridges this is a thoroughly modern settlement with a thoroughly urban population. It is split into two main halves by the geography of the lake, with the larger of the two - Tenochtitlan proper - accessible only by raised paths. In the hours of the rising sun the light reflects off the surface of the lake. It renders the white surfaces of the city's buildings almost painful to naked eyes.

The city divides into districts, the districts into regions, and each region needs maintenance. Sewage is removed by workers by hand, a ceramic aqueduct brings water for washing and cleaning from the sides of the lake. The more complicated your society, the tighter and more disciplined the maintenance systems have to be. With all this public space, and public architecture, the civil servant class buzzes around beneath the surface keeping society in tune. Complex societies are expensive, and need to be efficient to survive. This one was, and it didn't.

Forward 3 years

Things have not gone well. Frankly, he cannot believe how badly things done changed. His son died of plague just after planting season, and without the help this year’s maize is rotting in the fields for want of labour. He'd worry for his family, but his wife died within weeks of turning ill, after she went north to tend her mother on solstice. Now, there's only the daughter to provide for and she's started eating little more than the birds. The tribute demand hasn't flexed with the times the way it used to, and he needs to replicate the year before last's in weight or a mark will go down in a book. The collector is the same man, but he just looks on with a shrug when questioned, he has no influence with the newcomers above him. Worse, he had a brother in Tenochtitlan and now his eyes have hardened. Things are as bad everywhere, and the schools have shut because everyone is at home or in the fields.

After two hundred years of relentless progress, the writing is on the wall for everyone he ever knew. Collapse is hitting 10 million people squarely in the face. Change has been so fast he hasn't had a chance to stop and breathe. We Aztecs, we are staring into The Sun..

To the north of Mexico is California. Here grows the Sequoia, the world's heaviest tree. They weigh up to 2000 tonnes and many have lived for millenia. Their compressional strength is enormous, supporting their mass easily, but push them from the side and their shallow root structures collapse. The logs lie waiting to be incinerated in the next fertilising fire. They live a long life, but there are few of them overall.

In Meso-America in the two thousand years since the Olmec empire, every day had followed the last with the same rules. But a day was coming when they wouldn't.

600 men, 17 horses and 12 cannon are sailing towards the coast.