Zheng He's Treasure Fleet

The Admiral

In the year 1405, a fleet sailed from the port of Nanjing, China, and turned south into the open sea. It was the largest fleet the world had ever seen — or would see for another five hundred years.

The fleet contained 317 ships. The largest of them — the treasure ships (baochuan) — were approximately 120 metres long and 50 metres wide. For comparison, Columbus's largest ship, the Santa María, was 19 metres long. Zheng He's flagship was six times longer than anything Europe would produce for another century.

The admiral of this fleet was Zheng He — a Muslim eunuch from the province of Yunnan, captured as a boy during the Ming conquest of the south, castrated, and raised in the imperial court. He rose through the ranks through intelligence, loyalty, and physical imposingness (contemporary accounts describe him as over 2 metres tall).

Between 1405 and 1433, Zheng He commanded seven voyages across the Indian Ocean, visiting Southeast Asia, India, the Persian Gulf, the Red Sea, and the east coast of Africa. His fleet carried silk, porcelain, tea, and lacquerware for trade. It also carried 28,000 men — soldiers, sailors, translators, doctors, and merchants.

These were not voyages of exploration in the European sense — Zheng He wasn't looking for new worlds. The routes were known. The purpose was diplomacy and trade — to project Ming Dynasty power across the Indian Ocean and establish China as the centre of a tribute-based international order.

The Ships

The treasure ships were engineering marvels. Their size alone — if the Chinese accounts are accurate — represents a shipbuilding achievement not matched until the steel-hulled ships of the late 19th century.

The key innovation was the watertight bulkhead. Chinese shipwrights divided the hull into separate sealed compartments using transverse walls (bulkheads) that ran from the keel to the deck. If one compartment was holed — by a reef, a collision, or enemy action — water flooded only that compartment. The others remained dry, and the ship stayed afloat.

This technology did not reach European shipbuilding until the early 19th century, four hundred years later. When it did, it was inspired by observation of Chinese junks. Benjamin Franklin, who examined a Chinese-built ship, wrote in 1787 that European ships should adopt the bulkhead system. The technology was finally widely adopted after the sinking of the Titanic in 1912 — though even the Titanic's bulkheads didn't extend to the top deck, which is why the flooding cascaded over them.

The treasure ships also featured centreline rudders (which provide better steering than the side-mounted steering oars used by European ships), multiple masts (up to nine, carrying square and lateen sails for different wind conditions), and a flat bottom that allowed them to navigate shallow coastal waters and sit upright when beached for repairs.

Navigation

Zheng He's navigators used a combination of techniques:

The magnetic compass: China had been using magnetic compasses for navigation since the 11th century — two hundred years before the compass reached Europe. Zheng He's navigators used a 48-point compass (compared to the European 32-point compass), giving finer directional resolution.

Star altitude: Navigators measured the altitude of Polaris and other stars above the horizon using a simple device — a wooden board held at arm's length, with a string attached to the centre. The string was held between the teeth, ensuring a consistent distance between the eye and the board. Different marks on the board corresponded to different star altitudes, and thus different latitudes.

Sailing directions: Zheng He's expeditions produced detailed rutters (written sailing directions) called hǎidào zhēnjīng — "compass needle classics." These gave the compass bearing and number of watches (time periods) between successive waypoints, along with descriptions of landmarks, depths, and hazards. They were essentially medieval GPS coordinates — bearing and distance, in a pre-digital format.

The Cancellation

After Zheng He's death in 1433, the voyages stopped. The new emperor's Confucian advisors argued that the expeditions were wasteful — they cost the treasury enormous sums and brought back exotic gifts (giraffes, ostriches, zebras) but no meaningful revenue. The court faction that favoured northern land defence won out over the maritime faction.

In 1525, the Chenghua Emperor ordered the destruction of all records of Zheng He's voyages. The great ships were burned or left to rot. The technology was abandoned. China turned inward.

Within sixty years, European ships — tiny by comparison — would round Africa and begin building colonial empires across the very ocean that Zheng He had once dominated. Portuguese, Dutch, and British traders would establish the trade routes that Zheng He had pioneered, but with a very different purpose: not diplomacy but extraction.

The Engineering Question

The great unresolved question about Zheng He's fleet is: were the treasure ships really 120 metres long?

The Chinese historical sources consistently report this size. But no treasure ship has ever been found by archaeologists (a massive rudder post found in Nanjing in 1957 is the strongest physical evidence). Modern naval architects are divided: some argue that a wooden ship longer than about 70 metres would be structurally unsound — the forces of waves and wind would cause the hull to flex and the seams to open, a problem called hogging and sagging.

Others point out that the flat-bottomed junk design, with its watertight bulkheads acting as internal structural reinforcement, distributes forces differently than a European ship hull, and that 120-metre wooden ships might have been feasible with this design — though barely.

The debate is a lesson in naval architecture — the science of making a structure that is strong enough to survive the dynamic forces of the ocean, flexible enough not to crack, and light enough to float. Every ship is a compromise between these competing requirements, and the maximum size of a wooden ship is determined by the material properties of wood — its tensile strength, compressive strength, and resistance to shear — pushed to their absolute limits.

The end.