Hives, or Hive Cities, are a common sight throughout the galaxy. Their populations range from a few hundred million and into the billions - there are Hive Cities, particularly in Segmentum Solar, that have populations of tens of billions of people, perhaps even more than that (it is fiendishly difficultly to make an accurate census). And that is for just one city – some planets have numerous Hives of various sizes, for a total population that starts to exceed the imagination.

Image from unknown low pop-density Hive City

To those that have lived in a Hive, or even just visited one, it can be difficult to understand why man would want to crowd together like that. Well, man doesn't really want as much as he is governed by what he must do. Hives are just about the only practical way of harnessing a population of such staggering sizes. Hives are, in short, the most economical way of keeping people alive and productive. The amount of energy, food, water, transportation, sanitation etc. needed per capita is vastly lower in a Hive City than in any other form of human settlement.

Hives are also very easily defended. Massive armored shells or barrier walls are the norm, with endless defensive weapons emplacements scattered across the perimeters. The Hive itself, with its labyrinthine structure and endless supply of manpower is also a great defensive asset; taking a Hive by force requires an expenditure of military assets that would baffle even the most hardened commander.

The compact nature of the Hive also means its 'small' enough in terms of a space/energy ratio to be effectively shielded. Although big Hives can cover thousands of square miles, this is nothing compared to the area covered by an entire planet. Although there are tales of entire planets shielded by forbidden machines from the Dark Age of Technology, such feats are beyond the limits of current Imperial engineering. But Hives can be shielded and frequently are; an unshielded Hive is nothing but a death trap waiting for the enemy to unleash high-yield strategic weapons.

Hives can also protect against a hostile environment. Some Hives are located on barely-habitable worlds, and only the life-support systems of the Hive keep its occupants alive. Other Hives are located on worlds thoroughly raped by man for millennia; these places may have been garden worlds once, but thousands of generations of mining and industrial activity have rendered them barren or inhospitable.

Which brings us over to an oft-overlooked aspect of Hives; many are largely self-sufficient. Despite horror-stories about starving Hives isolated by Warp-storms, many Hives can manage quite well on their own, at least for a time. Take food production for example; although most Hives import vast quantities of food from off-planet, this is often low-bulk or luxury goods. The majority of food production takes place in the Hives soaring hydroponic spires or in deep faux-flesh vats. Water is extracted using a variety of methods, and everything is thoroughly recycled. Many Hives sit atop mineral-rich areas, and mines have been sunk deep into the planetary crust. The same goes for energy and waste; energy is oft geothermal or created by huge fusion plants, while waste that cannot be reclaimed are stored deep below ground or even hurled into the planetary core. Of course, being self-sufficient doesn't make the Hive's rulers rich, so a Hive will always be linked in terms of industry and commerce to other Hives and worlds. But an isolated Hive won't simply die overnight either.

Hive also offer a way of keeping the population under control. So the Hive keeps people in, just as much as it keeps enemies out. And while it is indeed impossible to monitor or police the teeming masses, it is still infinitely easier and most importantly much cheaper, than had the population been scattered across an entire planet!

Hives then, are the Imperium's way of keeping its teeming billions alive, productive, protected, and under control. No more, no less. And as there are no other viable alternatives things are not likely to ever change. Hives exist in Calixis, but only the Hives of Malfi (and possibly the two major Hives of Scintilla) are big enough to be worthy of comparison to the Hives of Segmentum Solar...and even they fare poorly, being small and unimportant in against a galactic backdrop. Nevertheless, the Hives of Calixis will play an important part in the upcoming campaign...