The Art of War for Trading — Chapter 3: Strategic Attack — Spread, Depth & Market Impact

"To win a hundred victories in a hundred battles is not the highest excellence; the highest excellence is to subdue the enemy without fighting at all." — Sun Tzu

Strategic & Financial Context

Strategic Attack is about winning at minimum cost. Sun Tzu ranks the options: thwart plans first, then alliances, then armies, and only last besiege a fortified city.

In markets, "besieging a city" means buying into heavy overhead supply, or shorting a bull-market advance. Skilled traders seek the line of least resistance.

In Chapter 3 of our Sun Tzu and the US Stock Market series, "strength" and "weakness" describe the supply structure — how much trapped stock sits overhead. This chapter addresses the layer beneath it: strength and weakness in the order book, meaning liquidity. Supply structure determines whether price can rise; liquidity determines what price you actually get the instant you press the button. The first is judgment; the second is execution — and good judgment executed badly still hands your money to someone else.

Wall Street Application

1. Avoiding Overhead Supply

• Strength: prior high-volume zones, trapped-holder peaks, declining long-term moving averages.
• Weakness: all-time highs with no overhead supply; clean right-side breakouts.

2. "Know the Enemy and Know Yourself"

3. Strength and Weakness in the Order Book

• Bid: the highest price someone will currently pay
• Ask: the lowest price someone will currently accept
• Spread: the difference — the price of liquidity itself

Tight spreads with heavy resting size are "weak points": easy to enter and exit. Wide spreads with thin books are "fortified": the wall is not trapped supply, it is the liquidity itself.

Depth matters more than spread, and most traders only look at the spread. A stock may quote a one-cent spread with only 200 shares at the offer. Buy 2,000 and the first 200 fill at the quote while the rest walk up through successive levels. Your average price is materially worse than the "ask" you saw. That difference is market impact, and it appears on no statement.

4. Who Pays for "Immediately"

The spread is the fee for immediate execution.

A market order announces: "any price is acceptable." In liquid large caps that is cheap. In small caps, pre/post-market, or the instant an earnings release crosses, it can cost several percent. That is "besieging the city" — paying the most expensive possible price for a result obtainable far more cheaply.

5. The Three Worst Moments for Liquidity

• The first five minutes: overnight orders flood in and spreads are among the day's widest. Novices place market orders precisely here.
• The earnings release itself: market makers pull quotes when informed traders may be present; spreads can widen tenfold.
• Pre- and post-market: few participants, minimal depth; a modest order moves price several percent.

All three are the moments when news is most exciting and acting immediately feels most urgent. Peak emotion coincides exactly with trough liquidity — not by coincidence but because they are the same phenomenon. "Subduing without fighting," at the order book, means simply not trading in these windows.

Execution Rules

1. Never besiege: don't buy size directly beneath heavy overhead supply.
2. Seek the vacuum: favor leaders breaking to new highs with no trapped supply above.
3. Stay in your circle: when the structure is unreadable, decline the engagement.
4. Read depth, not just spread: confirm resting size can absorb your order.
5. Avoid the opening five minutes and the earnings print: let spreads converge. The premium paid for haste often exceeds the trade's entire expected profit.
6. Default to limit orders: keeping the "what will I pay" decision yourself is the most concrete form of "causing others to move rather than being moved."

Relevance to a Retirement Portfolio

Retirees should follow "subdue without fighting" — do not skirmish with volatility. A diversified low-cost index portfolio captures long-run global growth without requiring any top or bottom to be called.

Liquidity mechanics have one very concrete retirement application: the timing of rebalancing and withdrawals. A portfolio rebalanced annually with limit orders during liquid hours pays almost nothing in friction. A portfolio forced to liquidate with market orders on a panic day sells at the worst price, across the widest spread, in the largest quantity — three losses at once.

This is the real argument for a cash buffer. Its purpose is not higher returns but ensuring you never have to be a seller at the moment liquidity is worst. Sun Tzu's highest excellence is not having to fight; for a retiree, the highest execution is not having to execute on the market's schedule.