7 Famous Straits That Shaped World History

I have a soft spot for straits. Every one of them is a bottleneck, and bottlenecks are where history gets interesting, because everybody has to queue up in the same narrow place and be visible while doing it. Here are seven with the best stories, one memorable fact each, in the order that makes the best dinner party sequence.

1. Gibraltar: the edge of the world, and the biggest waterfall that ever existed

The Greeks called the rocks either side of it the Pillars of Hercules and treated it as the frontier of the mapped world. Beyond lay ocean, weather and rumours. The pillars became a boundary marker so famous that Spain later put them on its coat of arms, wrapped in the motto plus ultra, further beyond, once it turned out there was quite a lot further beyond.

Here is the fact I cannot stop telling people. Around five and a half million years ago the Mediterranean had been cut off from the Atlantic long enough that much of it had evaporated into salt flats and deep dry basins. Then the barrier at Gibraltar gave way. Geologists call the result the Zanclean flood, and current reconstructions suggest the Mediterranean refilled with astonishing speed, water pouring through the gap on a scale that makes every waterfall now on earth look like a garden feature. The strait is nine miles of water that once ended a geological era.

2. Hormuz: the world's most watched 21 miles

About 33 kilometres wide at the pinch, with shipping lanes only a couple of nautical miles across, and roughly a fifth of globally traded oil goes through it because most of the great exporters sit inside a nearly enclosed sea with one door.

The surprising part is how old the arithmetic is. The island of Hormuz gave its name to a medieval trading kingdom that grew rich taxing goods moving between India, Arabia and Persia, and Portuguese fleets seized it in 1515 as part of a deliberate strategy of holding narrow points rather than oceans. Same choke, different cargo, five centuries apart. Full mechanics in the Strait of Hormuz explained.

3. Malacca: the shortcut that built a city state

The Strait of Malacca is the fast route between the Indian Ocean and the Pacific, threading between Sumatra and the Malay Peninsula. It narrows dramatically at its southeastern end and carries a huge share of trade between Europe, the Middle East and East Asia.

My favourite detail is the monsoon. For centuries the winds reversed seasonally, which meant ships arriving from the west could not simply carry on. They had to wait for the turn. So a place appeared where everyone waited, and where waiting merchants traded with each other rather than sit idle. Warehouses followed, then finance, then law. Singapore's rise is the modern chapter of a very old habit, and the deeper logic is in why port cities rule the world.

4. The Bosphorus: a strait with a city built across it

Under a kilometre wide at its narrowest, the only maritime exit from the Black Sea, and the boundary between two continents. Greek colonists founded Byzantium beside it in the seventh century BC. Constantine made it an imperial capital in 330. The Ottomans took the city in 1453 after building fortresses facing each other across the water so that no relief fleet could get through.

The detail people remember is the chain. The Byzantines strung a heavy iron chain on wooden floats across the Golden Horn to lock out enemy fleets, which worked so well that attackers resorted to dragging ships overland to get past it. There is a whole story in the Bosphorus, the strait that made and unmade empires.

5. Dover: 21 miles that ruined several excellent plans

The Strait of Dover is the narrow eastern end of the English Channel, and on a clear day you can see France from Kent. It is also the most successful defensive feature in European history, purely by existing.

The Spanish Armada of 1588 was undone as much by weather and logistics in these waters as by battle. Napoleon assembled an invasion army and a flotilla at Boulogne and never crossed. In 1940 an invasion was planned and shelved. A strait you can see across has still repeatedly proved unwise to cross with an army, because a narrow sea is not a small sea when you are moving horses, cannon and supply.

The consolation prize for everyone who wanted a link: the Channel Tunnel opened in 1994 and simply went underneath the argument.

6. Magellan: the only way around, for 367 years

The Strait of Magellan cuts through the southern tip of South America, a maze of channels, islands and abrupt weather that Ferdinand Magellan's expedition threaded in 1520. It was miserable sailing, but it was better than the alternative, Cape Horn, where the Southern Ocean funnels between continents and Antarctica and generates some of the worst seas anywhere.

The lovely fact is what happened to it. Until the Panama Canal opened in 1914, this cold, difficult passage was one of the world's most important trade routes, and towns along it grew wealthy on ships that had no choice. Then a canal opened 6,000 kilometres north, and the traffic evaporated almost overnight. Straits can be demoted.

7. Bering: where you can step into yesterday

The Bering Strait is about 82 kilometres wide and shallow, only some 50 metres deep in places. During the last glacial period, with so much water locked into ice sheets, the sea floor was exposed as a broad plain, and that land bridge is central to how people and animals moved into the Americas.

Then there is my favourite piece of trivia on the entire planet. In the middle of the strait sit two islands, Big Diomede and Little Diomede, roughly four kilometres apart, with the International Date Line running between them. They are nicknamed Tomorrow Island and Yesterday Island, because crossing that short gap changes the calendar date. Two islands, same weather, different day.

What straits teach you in about two minutes

Every entry above is really the same story. Water is the cheap way to move heavy things, narrow water is where the cheap way is forced into a queue, and queues can be taxed, defended, blocked or missed entirely when technology changes the route. Learn the shape of a few straits and an alarming amount of history stops feeling arbitrary.

This is exactly the sort of thing we make for MindSnap, our app: two minute lessons that hand you the structure of something rather than a list of dates, across five flagship story-driven collections plus unlimited topics you can request. Disclosure: MindSnap is our app. If chokepoints are your genre, keep going with maritime chokepoints explained, or pick a subject from our topics.

Nobody builds a fortune in the middle of an ocean. They build it where the ocean narrows.