“Therefore a wise prince will seek means by which his subjects will always and in every possible condition of things have need of his government, and then they will always be faithful to him.”
— Niccolo Machiavelli, “The Prince”, Datalinks
Doctrine: Loyalty is the only doctrine technology that is labeled as a pure military technology as opposed to an exploration one. Correspondingly, it’s also the only one that doesn’t grant a new type of unit locomotion. Instead, Doctrine: Loyalty enables the construction of the Perimeter Defense base facility, the Command Nexus secret project, and the Police State social engineering choice.
On the tech tree, it’s a second-tier technology that relies on Social Psych and Doctrine: Mobility. Which makes it especially interesting that Chairman Yang and the Hive begin with this technology. All of the other initial technologies possessed by the other factions are at the first tier. Only the Hive starts with a technology for which they do not possess the prerequisites.
These seemingly disparate gameplay facts provide an interesting context to the provided quote. Doctrine: Loyalty is best seen as the literal instantiation of Machiavelli’s lesson, applied to the early colonization effort on Planet. It’s not hard to imagine that the fixed, centrally-supported Perimeter Defenses make for a tangible reminder of the subjects’ dependence upon the government and upon each other. Fear of the unknown and of the outgroup are the classic building blocks of effective loyalty, after all.
Taking this advice to its utmost results in the adoption of the Police State political social engineering choice. In SMAC, a Police State gives bonuses to the faction’s police and unit support ratings in exchange for an efficiency penalty. A higher police rating allows the faction to assign more troops per base to drone suppression and can improve the per-unit effects, while the unit support bonus allows more units per base to be supported without incurring additional mineral costs.
Taking these together, the obvious way to take advantage of these benefits is to build a larger military instead of spending minerals on drone suppression base facilities or energy on the Psych budget. But the larger military has other benefits: it can be used to deter aggression on the part of the mind worms or rival factions; it does not directly cost energy to maintain; it is not vulnerable to spy sabotage; and it can potentially be shifted to the attack.
The negative to efficiency is particularly painful, though. For most factions, it means that it is virtually impossible to pair it with a Planned economy, because the double efficiency penalty leads to virtual economic collapse and lots of extra drones. Only the Hive (who are immune to negative efficiency) and the Gaians (who have an innate efficiency bonus) can do this.
It also reduces the benefit of pairing this with a Free Market economy. More of the new energy is lost to inefficiency. And the police bonus partially cancels out the large police negative for running Free Market, but it isn’t enough for any faction but the Spartans (with their police bonus) to completely remove the pacifism penalty from stationing military units outside the faction’s borders. That makes it a lot harder to threaten a rival faction.
It only really works great with a Green economy. An ecologically-minded Police State trades the efficiency penalty for a more manageable growth penalty. But, in exchange, it’s an excellent war-focused setup. The faction that runs this combination gets more units for the attack, an excuse to spend less on infrastructure, and the ability to gather native mind worms to supplement the offensive.