# The Age of Sea Empires > Zheng He's fleets turn back and Portuguese ships reach India and Malacca; Spain links the world with the Manila galleons; the Atlantic slave trade; the Dutch and English companies and cosmopolitan Ayutthaya; British India and the Opium Wars; then Siam between British Burma and Malaya and French Indochina: the Bowring Treaty of 1855, the crisis of 1893 and the treaties of 1904, 1907 and 1909, with both the 'lost territories' and the 'Siam Mapped' views; and the British Empire at its 1920 peak. Episode 12 of the World Empires series. Interactive film: https://www.planetpast.com/stories/empires-sea-empires/ Publisher: PlanetPast (https://www.planetpast.com/) · Published 2026-10-13 · History ## Prologue ### The Age of Sea Empires *World Empires · Episode 12* How oceans became highways of power. Between 1405 and 1433, the Ming admiral Zheng He led seven great fleets across the Indian Ocean, as far as Arabia and East Africa, with hundreds of ships. They collected tribute and gifts, then stopped. The Ming court turned inward. Within decades, much smaller European ships would arrive in the same waters and stay. Prologue · Episode 12 of the World Empires series #### Zheng He’s fleets - **Voyages**: 7 1405–1433 - **First fleet**: ~300 ships reported; sizes debated The fleets called at Ayutthaya, Malacca and Calicut. Grey outlines show other powers of the time. Outlines are approximate. Sources: [Wikipedia: Ming treasure voyages](https://en.wikipedia.org/wiki/Treasure_voyages) ## Chapter I · Oceans opened ### Portugal sails east *Chapter I · 1488–1511* Around Africa to the spice markets. Portuguese sailors worked their way down the African coast. In 1488 Bartolomeu Dias rounded the Cape of Good Hope; in 1498 Vasco da Gama reached Calicut in India. With armed ships, Portugal seized key ports: Goa in 1510 and Malacca in 1511, controlling the straits between the Indian Ocean and the South China Sea. In 1511, the first European envoy to Ayutthaya, Duarte Fernandes, was sent from Malacca. Portuguese traders and soldiers were soon serving the Siamese king. Chapter I · Step 1 #### Portugal sails east - 1488 Dias rounds the Cape - 1498 Da Gama at Calicut - 1510 Goa taken - 1511 Malacca taken; first envoy to Ayutthaya Sources: [Wikipedia: Portuguese Empire](https://en.wikipedia.org/wiki/Portuguese_Empire); [Wikipedia: Ayutthaya Kingdom](https://en.wikipedia.org/wiki/Ayutthaya_Kingdom) ### The first global trade *Chapter I · 1492–1600* Silver across the Pacific. After Columbus reached the Caribbean in 1492, Spain and Portugal divided the world beyond Europe between them by the Treaty of Tordesillas in 1494. In 1571 Spain founded Manila. Every year, galleons crossed the Pacific between Manila and Acapulco, carrying American silver west and Chinese silk and porcelain east. For the first time, every inhabited continent was linked by regular trade. Much of the silver mined in Bolivia and Mexico ended up in China. Chapter I · Step 2 #### The first global trade - 1494 Treaty of Tordesillas - 1565–1815 Manila galleons - 1571 Manila founded as a Spanish city Sources: [Wikipedia: Manila galleon](https://en.wikipedia.org/wiki/Manila_galleon) ### The Atlantic slave trade *Chapter I · 1500s–1860s* The darkest trade of the sea empires. Plantations of sugar, tobacco and later cotton in the Americas were worked by enslaved Africans. Between the 1500s and the 1860s, about 12.5 million Africans were forced onto European and American ships. Around 1.8 million died during the crossing. Britain abolished the trade in 1807 and slavery in its colonies in 1834. Brazil, the last country in the Americas, abolished slavery in 1888. Chapter I · Step 3 #### The Atlantic slave trade - **Embarked**: ~12.5M SlaveVoyages estimate - **Arrived**: ~10.7M Sources: [SlaveVoyages: Trans-Atlantic slave trade estimates](https://www.slavevoyages.org/assessment/estimates) ## Chapter II · Companies ### Companies with armies *Chapter II · 1600–1688* And a cosmopolitan Ayutthaya. The English East India Company was founded in 1600, the Dutch VOC in 1602. These were private companies that could raise armies, make treaties and rule territory. The VOC made Batavia, today’s Jakarta, its Asian base in 1619. Ayutthaya traded with them all. A VOC post opened there in 1608, and a Siamese embassy reached the Netherlands the same year. Japanese, Persian, Chinese and Portuguese communities lived in the city. King Narai exchanged embassies with Louis XIV of France; Kosa Pan’s mission reached Versailles in 1686. After a revolution in 1688, Siam expelled the French garrisons and kept Europeans at a distance. Chapter II · Step 4 #### Companies with armies - 1600 English East India Company - 1602 Dutch East India Company (VOC) - 1608 VOC in Ayutthaya; Siamese embassy to the Netherlands - 1686 Kosa Pan at Versailles - 1688 Siamese revolution; French expelled Sources: [Wikipedia: Dutch East India Company](https://en.wikipedia.org/wiki/Dutch_East_India_Company); [Wikipedia: Ayutthaya Kingdom](https://en.wikipedia.org/wiki/Ayutthaya_Kingdom) ### A company conquers India *Chapter II · 1757–1858* From traders to rulers. As the Mughal Empire weakened, the British East India Company won the Battle of Plassey in 1757 and took control of Bengal, India’s richest province. Over the next century, through wars and alliances, the Company came to rule most of India, with an army largely of Indian soldiers. After a great uprising in 1857, the British government abolished the Company’s rule. From 1858 India was ruled directly by the British Crown. Chapter II · Step 5 #### A company conquers India - 1757 Plassey - 1765 Company collects Bengal’s revenue - 1857 Indian Rebellion - 1858 Crown rule (the Raj) Sources: [Wikipedia: Company rule in India](https://en.wikipedia.org/wiki/Company_rule_in_India) ### The Opium Wars *Chapter II · 1839–1860* Gunboats open China. Britain bought tea from China but had little China wanted. Its merchants smuggled opium from India instead, and millions in China became addicted. When China’s official Lin Zexu destroyed British opium in 1839, Britain went to war. The Treaty of Nanjing in 1842 gave Britain Hong Kong and opened Chinese ports. After a second war, by 1860 China had signed what it still calls “unequal treaties”, the model that would soon reach Siam. Chapter II · Step 6 #### The Opium Wars - 1839–1842 First Opium War; Treaty of Nanjing - 1856–1860 Second Opium War “Unequal treaties” typically fixed low tariffs and gave foreigners extraterritoriality: the right to be tried by their own consuls. Sources: [Wikipedia: First Opium War](https://en.wikipedia.org/wiki/First_Opium_War) ## Chapter III · Siam between empires ### Closing in *Chapter III · 1819–1887* Britain from the west, France from the east. Britain took Penang in 1786 and founded Singapore in 1819. In three wars, in 1824, 1852 and 1885, it conquered all of Burma. France took Saigon in 1859, made Cambodia a protectorate in 1863, and by 1887 had joined Vietnam and Cambodia into French Indochina. By the late 1880s, Siam was the only independent kingdom left between British Burma and Malaya and French Indochina. Chapter III · Step 7 #### Closing in - 1819 Singapore - 1824–1885 Three Anglo-Burmese wars - 1863 French protectorate over Cambodia - 1887 French Indochina The yellow outline shows Siam together with the Lao, Khmer and Malay lands that owed it tribute; the nature of those ties is discussed below. Sources: [Wikipedia: British Empire](https://en.wikipedia.org/wiki/British_Empire) ### The Bowring Treaty *Chapter III · 1855* Opening Siam without a war. King Mongkut, Rama IV, had watched China’s defeat. In 1855 he signed a treaty with Britain’s envoy John Bowring rather than risk war. It limited Siam’s import duties to 3 percent, ended royal trade monopolies, and gave British subjects extraterritoriality. Similar treaties with other Western powers followed. Rice exports boomed and Bangkok grew. But Siam had lost control over part of its own laws and taxes, which it would take until the 1930s to fully regain. Chapter III · Step 8 #### The Bowring Treaty - **Signed**: 18 Apr 1855 - **Import duty cap**: 3% - **Also**: extraterritoriality; free trade; end of royal monopolies Sources: [Wikipedia: Bowring Treaty](https://en.wikipedia.org/wiki/Bowring_Treaty) ### Borders drawn by treaty *Chapter III · 1893–1909* Siam’s map takes its modern shape. In 1893, after a clash on the Mekong, French gunboats forced their way past the forts at Paknam to Bangkok. Siam gave up all claims east of the Mekong, most of today’s Laos. In 1904 Siam ceded lands on the Mekong’s right bank. In 1907 it ceded Battambang, Siem Reap and Sisophon to French Cambodia, and France gave up legal privileges over its Asian subjects in Siam. In 1909 Siam transferred Kedah, Perlis, Kelantan and Terengganu to Britain, in return for a loan for the southern railway and limits on British extraterritoriality. Chapter III · Step 9 #### Borders drawn by treaty - 1893 Paknam incident; lands east of the Mekong to France - 1904 Right-bank Mekong lands to France; French troops leave Chanthaburi - 1907 Battambang, Siem Reap, Sisophon to France; Trat and Dan Sai returned to Siam - 1909 Kedah, Perlis, Kelantan, Terengganu to Britain Areas and boundaries here are simplified. Exact lines were set by later boundary commissions, and some are still disputed. Sources: [Wikipedia: Franco-Siamese crisis of 1893](https://en.wikipedia.org/wiki/Franco-Siamese_crisis); [Wikipedia: Franco-Siamese Treaty of 1907](https://en.wikipedia.org/wiki/Franco-Siamese_Treaty_of_1907); [Wikipedia: Anglo-Siamese Treaty of 1909](https://en.wikipedia.org/wiki/Anglo-Siamese_Treaty_of_1909) ### How Siam stayed independent *Chapter III · 1868–1910* And two ways of telling the story. Siam survived as a buffer between Britain and France, which in 1896 agreed to guarantee the Chao Phraya basin. King Chulalongkorn, Rama V, reformed fast: ministries, provinces, railways, schools, and the gradual abolition of slavery. Thai textbooks often tell this period as one of “lost territories”, given up to save the core of the country. The historian Thongchai Winichakul argues that before modern maps, sovereignty in the region was layered and shared. Many of those lands had their own rulers, and Bangkok itself was tightening control over Lanna, Isan and Patani at the same time. Both views agree on one thing: the modern borders of Thailand, Laos, Cambodia and Malaysia were fixed in these years by treaties with European empires. Chapter III · Step 10 #### How Siam stayed independent - 1868–1910 Reign of Chulalongkorn (Rama V) - 1896 Anglo-French declaration on Siam - 1874–1905 Gradual abolition of slavery - 1938 Last unequal treaties revised Siam was never colonised, but some scholars describe its position as “semi-colonial”: independent, but bound by unequal treaties. Sources: [Wikipedia: Thongchai Winichakul, Siam Mapped (1994)](https://en.wikipedia.org/wiki/Siam_Mapped); [Wikipedia: Franco-Siamese Treaty of 1907](https://en.wikipedia.org/wiki/Franco-Siamese_Treaty_of_1907); [Wikipedia: Anglo-Siamese Treaty of 1909](https://en.wikipedia.org/wiki/Anglo-Siamese_Treaty_of_1909) ## Chapter IV · High noon ### High noon of empire *Chapter IV · 1884–1920* Africa divided; a quarter of humanity under one flag. At a conference in Berlin in 1884 and 1885, European powers set rules for claiming Africa. By 1914 almost all of Africa was under European rule; only Ethiopia, which defeated Italy at Adwa in 1896, and Liberia stayed independent. After the First World War, the British Empire reached its greatest size: about 35 million square kilometres, and roughly a quarter of the world’s people. It was the largest empire in history. Within fifty years, it would almost be gone. Chapter IV · Step 11 #### High noon of empire - **British Empire, 1920**: ~35.5M km² largest in history - **People**: ~¼ of humanity - **Independent in Africa, 1914**: Ethiopia and Liberia Sources: [Wikipedia: Scramble for Africa](https://en.wikipedia.org/wiki/Scramble_for_Africa); [Wikipedia: British Empire](https://en.wikipedia.org/wiki/British_Empire); [Wikipedia: List of largest empires](https://en.wikipedia.org/wiki/List_of_largest_empires) ## Epilogue ### A world linked by sea *Epilogue* The modern map was drawn in this age. Sea empires linked the world into one economy, spread crops, languages and religions, and drew most of the borders on today’s map. They also brought conquest, slavery and famine, and in many places their legacies are still argued about. Next, the final episode: how the empires ended, from 1918 to today. Epilogue #### A world linked by sea - 1498 Da Gama reaches India - 1571 Manila: a trade route around the world - 1757 Plassey - 1855 Bowring Treaty - 1909 Siam’s modern borders - 1920 British Empire at its peak #### The series - **00**The Rise and Fall of Empires (overview) - **01**The First Empires: Mesopotamia - **02**Egypt of the Pharaohs - **03**Persia and Alexander - **04**The Maurya Empire of India - **05**China Unified: Qin and Han - **06**Rome - **07**The Islamic Caliphates - **08**The Khmer Empire of Angkor - **09**The Mongol Empire - **10**The Ottoman Empire - **11**The Aztec and Inca Empires - **12** The Age of Sea Empires (this film) - **13**The End of Empires The still images on the chapter cards are AI-generated illustrations. Outlines are approximate and simplified. Sources: [Wikipedia: British Empire](https://en.wikipedia.org/wiki/British_Empire); [Wikipedia: Portuguese Empire](https://en.wikipedia.org/wiki/Portuguese_Empire); [Wikipedia: Thongchai Winichakul, Siam Mapped (1994)](https://en.wikipedia.org/wiki/Siam_Mapped)