“From a position of this sort, if the enemy is unprepared, you may sally forth and defeat him; but if he is prepared, disaster will ensue.”
This ground cuts both ways; strike only if he is unprepared, else the trap closes on you.
Chapter 10’s second ground: entangling terrain, from which sallying forth defeats an unprepared enemy — but if he is prepared, disaster ensues. The ground is symmetric: it punishes whoever commits second. Entangling ground is any position that is easy to enter and costly to leave, which is why Sun Tzu’s rule reduces to a single variable: preparation asymmetry, which in practice means surprise.
A company enters a country market via an exclusive local partner — easy to sign, structurally painful to exit (contracts, localization, brand association). If the incumbent players are asleep, the entry wins outright. If they are awake and prepared, the newcomer is now tangled in a partnership it cannot leave, on terms set by people who watched it coming. Same move; the entire outcome was decided by the surprise variable before entry.
Entangling ground is not bad ground — the verse explicitly says you may defeat an unprepared enemy from it. The discipline is the pre-check: is he prepared? Companies entangle themselves through optimism, entering because the deal is available rather than because the surprise exists. The ground forgives everything except entering it unaware.