The Use of Spies

This is the thirteenth and final chapter-length entry in a series applying Sun Tzu’s Art of War to marketing and search strategy. The Attack by Fire covered specialized tactics that only work under the right conditions. This chapter closes the arc with something that, on reflection, every previous chapter quietly assumed: none of it works without genuine knowledge of the actual situation, and that knowledge doesn’t arrive on its own.

Sun Tzu opens with an argument about cost that’s easy to underestimate. Raising an army of a hundred thousand men, he notes, means daily expenditures on a massive scale — the ruin of households, the exhaustion of a country’s strength, hundreds of thousands of families kept from their work for years, all in pursuit of a single decisive victory. And yet, he says, a ruler who begrudges the comparatively small expense of paying for good intelligence, and as a result remains ignorant of the enemy’s actual condition, is guilty of the height of inhumanity. The knowledge that would have prevented the waste was available, cheaply, and wasn’t paid for.

Knowing costs less than not knowing

This is the argument the whole chapter builds from: genuine intelligence is, relative to the cost of acting without it, extraordinarily cheap. Sun Tzu isn’t making a moral point for its own sake — he’s making an economic one, dressed as a moral one. The actual waste isn’t the cost of gathering good information. It’s the cost of every decision made without it, compounding across a campaign that intelligence could have shortened, redirected, or avoided entirely.

This translates almost without adjustment into marketing operations, where genuine research into a buyer’s actual world, a competitor’s actual position, or a category’s actual current state is frequently treated as a cost to be minimized, while the compounding cost of campaigns built on partial or assumed knowledge goes largely untracked, because it’s distributed across many smaller decisions rather than appearing as one visible line item.

Foreknowledge cannot be extracted from spirits or patterns

He’s specific, and slightly dismissive, about where real intelligence doesn’t come from: not from spirits, not from analogy with past events, not from calculation. It can only come from people — specifically, from those who have direct knowledge of the enemy’s actual situation.

This is a pointed distinction worth sitting with. It’s tempting, in marketing, to treat pattern-matching against historical campaigns, or general industry benchmarks, as a substitute for genuinely current, specific knowledge of an actual buyer or an actual competitor’s actual present state. Sun Tzu’s argument is that these are structurally different categories of knowledge, and the second can’t be derived from the first. A well-reasoned analogy to a past success is not the same as actual, current information about the specific situation in front of you, and treating it as an adequate substitute is exactly the failure this chapter is written against.

The five kinds of intelligence source

Sun Tzu categorizes intelligence sources into five types: local spies, drawn from the enemy’s own country; inward spies, drawn from the enemy’s own officials; converted spies, originally the enemy’s own agents who’ve been turned; doomed spies, deliberately given false information to spread, expecting they may be captured; and surviving spies, who return with genuine information after passing through the situation and back.

The categories translate more usefully than they might first appear. Local sources are the people genuinely embedded in a market or a buyer’s world — not surveyed from outside, but actually part of it. Inward sources are relationships with people close to a competitor or a category’s actual decision-making, rather than only what a competitor publishes externally. Converted sources are former competitors, former clients of a competitor, or people who’ve moved between organizations and carry real, specific knowledge with them. Doomed sources have a less literal but real analogue in deliberate public positioning meant to test or provoke a reaction, revealing something about a competitor’s actual state through how they respond. And surviving sources — the ones who go into the situation and return with a genuine, current report — are the closest analogue to genuine, first-hand immersion: someone who has actually spent time in the buyer’s or competitor’s actual world and come back with something real, rather than reconstructed secondhand.

The double agent, and the value of information nobody else has

Sun Tzu treats converted spies as the most valuable category, and his reasoning is worth sitting with directly: because it’s through them that local and inward sources can be recruited, and through them that a doomed source’s false information can be believably transmitted to the enemy, and through them that a surviving source can be used at the right moment. Nearly every other kind of intelligence, in his accounting, depends on first having someone who genuinely understands both sides.

The marketing equivalent of the converted spy is someone who has genuinely worked inside both a buyer’s world and the vendor’s world — a former practitioner who now sells to practitioners, someone who has actually held the job the buyer holds before moving into service of that buyer’s category. This is a specific argument for why that kind of person is disproportionately valuable, not just as a hire but as an intelligence source: they can interpret signals from both sides that someone with experience of only one side would misread or miss entirely.

Intelligence has to actually change the decision

There’s a specific instruction late in the chapter that closes the loop on everything before it: whatever the army wants to attack, whatever positions it wants to strike, whatever individuals it needs to identify — the names of the commanding officers, their aides, their household staff, their gatekeepers all need to be found out in advance, through deliberate intelligence work, not guessed at.

The point being made isn’t just “gather information generally,” it’s that intelligence has to be specific enough to actually change a real, upcoming decision, not general enough to just create a comfortable sense of being informed. A category-level understanding of a competitor is not the same as knowing the specific thing that would actually change what you do next. Sun Tzu’s insistence on names, specifics, and actual operational detail is a case against intelligence gathering that produces broad awareness without producing anything that alters a real choice.

Why this chapter comes last

It would have been possible to open this whole series with this chapter, given how much every previous one depends on it — Laying Plans’ honest assessment, Attack by Stratagem’s knowledge of both sides, Weak Points and Strong’s ability to find undefended ground, The Army on the March’s reading of small signals. All of it assumes genuine intelligence was available to act on. Sun Tzu places it last instead, and I think the placement is deliberate rather than an afterthought.

By the time a reader reaches this chapter, twelve chapters of tactics, positioning, and posture have already been described in detail — and the final move is to reveal that none of it was ever free-standing. Every principle in this arc was downstream of information that had to be actively, deliberately gathered, at real cost, by people willing to pay for it rather than assume it. Ending here rather than starting here forces the realization that intelligence isn’t one input among many. It’s the thing every other chapter secretly required all along.

What this chapter, and the arc, asks

The specific instruction is to treat genuine intelligence — about buyers, about competitors, about the actual current state of a category — as one of the cheapest, highest-leverage investments available, precisely because its absence doesn’t show up as a single visible failure, but as a slow compounding of decisions made on incomplete information across every other chapter in this series. And the broader instruction, closing out the whole arc, is one Sun Tzu seems to want the reader to arrive at only after everything else: that assessment, positioning, timing, terrain, and posture were never separate disciplines. They were all expressions of how well, and how honestly, the underlying situation was actually understood before any of it began.