Four Places the Water Narrows

Some geography cannot be legislated away, and the same handful of places have appeared in strategic thinking for as long as there has been strategic thinking.

Roughly a fifth of the world's oil passes through the Strait of Hormuz, which at its narrowest is a corridor a few dozen kilometres across. Pipelines exist that bypass it and they carry a fraction of the volume. The Strait of Malacca carries an enormous share of seaborne trade towards east Asia through a passage that is long, narrow and shallow, and its existence explains a great deal of infrastructure investment in overland routes and alternative ports that would otherwise make no commercial sense at all.

The Suez Canal and the Bab el-Mandeb form a single route between Europe and Asia: interrupt either and traffic goes around Africa, adding thousands of kilometres and roughly a week and a half to every voyage.

The Panama Canal is the strangest of the four, because it runs on fresh water. Every transit releases water from an artificial lake fed by rainfall, so the number of ships that can pass in a day depends on the weather. Drought in 2023 and 2024 cut transits sharply, and no navy was involved. It is the one great chokepoint whose capacity is set by the climate.

Here is the mechanism that makes all four matter more than they appear to.

A chokepoint does not have to be closed to have effects. It has to be credibly threatened. Insurance underwriters reprice risk within hours; shipowners reroute; charter rates move; delivery schedules slip across an entire ocean. All of that happens on the possibility of interruption rather than on interruption itself, which means the party threatening pays almost nothing and the effect is immediate and wide.

That asymmetry, cheap to threaten and expensive to absorb, is what makes these places durable instruments of leverage, and it is why they do not need to be used to be useful.

Now put the five books of this course together, because the last thing worth taking from it is a shape rather than a fact.

In book two, power was concentrated in a palace, a general staff and a few hundred officers, which is what made a coup thinkable with four hundred and eighty men. In book three, attention concentrated in a handful of platforms, which made a single legal rule about liability more powerful than any amount of filtering equipment. In book four, an entire territory concentrated in the hands of one man, which removed every check that ordinarily applies to an empire. In this book, manufacturing concentrated on an island, communications on a seabed, chemistry in one country, and trade in four narrow stretches of water.

A system optimises. Concentration follows, because optimisation is concentration by another name. And then somebody notices that they are holding a lever, which they did not build and usually did not plan.

The lever is different every time. The shape is not. That is as close to a general law as this subject offers, and it is worth considerably more than any individual fact in it, including all the ones you have just learned.