Why India United but Southeast Asia Never Did | The Geography Behind History

If you were to draw a line starting from the western edge of Afghanistan, India, Bangladesh and then down through Myanmar, Thailand, Malaysia and Indonesia, and eventually I'll arrive at the Indonesian island of Bali, you'd be for the best part of a thousand years traveling through one continuous cultural zone which historians call the Sanskrit Cosmopolis. It's called this because there was so much similarity across the entire region from the style the temples were being built in, Just the general cultural similarity, as well as very importantly, the rule of Sanskrit. None of that ever meant that there was government or empire ruling over the entire region. It was a shared culture and not a unified kingdom. Roughly where Bangladesh ends and Myanmar starts, you see how both sides of that divide look very different historically. Let's start with India, the largest country in this region and the most populous country in the world with over 1.4 billion people. Look at a map and you have two seas that box in the triangle shape on either side, the Arabian Sea to the west and the Bay of Bengal to the east, both narrowing inward as they run south until they meet at India's southern tip. Follow that same triangle back up to its base and you hit the wall that closes the northern part off, the Himalayas. The Himalayas are without doubt the most impressive mountain range on earth, running 1500 miles end to end. Roughly the distance from London to Moscow and it holds 10 of the 14 mountains on earth over 8,000 meters high plus more than 50 separate peaks over 7,000 meters. This is the largest natural barrier anywhere on earth and it completely shuts the Indian subcontinent off from China and Tibet further north. There has never been a serious invasion of the subcontinent that has crossed the Himalayas from the north so that's a huge natural defense barrier. So that's the whole shape of the subcontinent, a single, largely self-contained landmass. Inside that wall sits the single most important piece of geography in this entire story, the Indo-Gangetic Plain. It's a flat, vast flood plain running roughly 1500 miles from what's now the Afghan border all the way to the Assam, which is the north-easternmost portion of India. And this plain is fed by three huge river systems, the Indus, the Ganges and the Brahmaputra. All three of them pouring down from the Himalayan rain and snowmelt above. It covers around 270,000 square miles, almost exactly the same size as the state of Texas, and it's one of the most fertile growing regions in the world. It functions pretty much as one continuous corridor of farmable, marchable, and most importantly, governable land. Whoever controlled this plain controlled the demographic and the agricultural heart of the entire subcontinent. Let's get into the history now about this region and when it was conquered. Chandragupta Maurya used this plain first, building out from a base in the Gangetic heartland to unify the northern and central subcontinent by 322BC, then pushing northwest as far as modern day Afghanistan. His grandson Ashoka went further, conquering the eastern kingdom of Kalinga, roughly where the modern state of Odisha sits today, and by the end of his reign, controlled everything Everything from Afghanistan and Balochistan in the northwest. Across Kashmir and Nepal, through Bengal, and down across almost the entire Indian subcontinent, stopping short only of the Tamil Kingdoms in the deep south and the Brahmaputra Valley in the north east. This was the very first time in history the whole subcontinent, or more or less, had ever answered to one ruler, and it was built entirely off that very important plain. That unity didn't outlast Ashoka by much though. Within decades, the empire broke apart and for the next 500 years, the plains split into a few different regional kingdoms, with nobody solely ruling over the whole of it. Then around 320 CE, the Guptas pulled it back together again, ruling directly across the same northern band from Punjab to Bengal and Assam, an estimated 2.2 million square miles, with kingdoms as far south as Kanjipuram paying tribute without ever being directly governed And then, roughly a thousand years after that, a completely different power did it again. The Delhi Sultanate, under Alauddin Khilji in the early 1300s, pushed south from the same Gangetic base all the way into the Deccan, which is the large central portion of India, making most of the major kingdoms of southern India into tribute-paying states. This was very similar to what the Guptas had managed centuries earlier And then again, 200 years later, Babur marched down through the exact same Northwest Corridor every invader before him had used, and founded the Mughal Empire, ruling once again from that same core plain. When the British eventually took over, they didn't invent a new shape either, because they didn't really have to. They inherited the same subcontinental outline and administered it as one. So that was five separate unifications across 2,000 years. What I would argue they all had in common, despite the desire to conquer and rule over a large area of land, was the geographical make-up of the subcontinent. None of these unification attempts would have been possible without it. The Himalayas weren't just a wall that kept invaders out, although that massively helped. They're the reason the plain beneath them is fertile at all. Monsoon winds sweeping off the Indian Ocean every summer and the Himalayas block them from ever escaping further north. Forcing them to dump their moisture onto the mountains and plains instead of passing harmlessly over into Tibet. And once that food rich flat corridor existed, everything else followed automatically. An army raised in the west could reach the east or south in weeks and without any major natural obstacles stalling the way. Tax revenue could flow back to a single capital just as fast. And very importantly for an empire, a rebellion anywhere on the plain could be found Before it had time to harden into its own kingdom, Rome had to defend three separate frontiers thousands of miles apart and collapse the moment it couldn't hold all of them at once. An Indian empire, on the other hand, only ever had to watch from one direction, because the mountains and the oceans were already doing the rest of the job for them. The key every time was controlling the plain, and with it, the ability to feed, communicate across it, and defend it. Now look at Southeast Asia because this is where the exact same starting ingredients produce a completely different result. 11 countries occupy Southeast Asia today and it's really worth splitting them into two groups straight away. Six of them, so Indonesia, the Philippines, Malaysia, Singapore, Brunei and East Timor are scattered across the water and it honestly barely needs explaining why an archipelago never became unified under one empire. The genuinely interesting half is the other five though, so Myanmar, Thailand, Laos, Cambodia and Vietnam, sitting on one connected mainland. Put together, that's roughly 1.4 million square miles of contiguous land, nearly three times the size of the Indo-Gangetic plain, the exact plain that helped the unification of the entire Indian subcontinent on and off for 2000 years. There was more than enough connected ground here to theoretically do the same, but it never did. Look at this topographical map of the mainland, and there are three separate mountain walls running roughly parallel to each other, north to south, and each one slicing straight through what would otherwise be one connected landmass. Starting here in the west, you have the Arakan Mountains, running for about 600 miles from the Indian border in the north, down to Cape Negri on Myanmar's southern coast, reaching 3,094 metres at their highest point, Mount Victoria. This is a natural wall inside Myanmar itself, cutting the country's own western coastline off from the Irrawaddy Valley and the rest of the interior of the country. Move east, and a second wall runs down the modern-day Myanmar-Thailand border. The Dawna and the Biloktowng together roughly 500 miles combined, peaking around 2,080 meters high. Everything west of it drains into Myanmar's river system, feeding the country's agricultural heartland. Everything east of it drains into the river that runs through Bangkok and feeds Thailand's central plain. Two entirely separate river civilizations, but one huge mountain wall apart. So it's probably starting to make sense why Southeast Asia never unified, because practically this meant that whichever kingdom rose to power on the Myanmar side, they had no simple or realistic way to project power over that wall into Thailand's river basin, and the same was true in the reverse on the Thai side. Move east once again and there's a third wall, the Annamite range, which is similar Similar in height to the Arakan range in Myanmar. They run down the present-day Laos-Vietnam border, running for roughly 800 miles from north-central Laos down through Vietnam almost to Saigon, reaching 2,890 metres at their highest point. This produced the exact same result. Two smaller civilisations could form on either side of this range, one built around the Mekong Basin on the Laos side and the other along Vietnam's own narrow coastal strip facing the South China Sea. Which incredibly in places is just 35 miles wide, but again holding power across that range was another matter entirely. So the awkward mountainous terrain was the first obstacle as to why mainland Southeast Asia never unified. The second reason isn't that the valleys which this region has, and there are four of them, themselves were too small. Each one was perfectly capable of feeding a major kingdom on its own. It's what sits in between these valleys which is important. For a kingdom based in Myanmar's valley to actually absorb Thailand's kingdom, or Cambodia's kingdom, for example, to take over Vietnam's land, it needed to march an army across the gap. which in itself will be challenging given what we have just learned about the mountain ranges. Then to keep that army fed and administered well enough to hold the ground permanently and that meant the land in between needed to be able to grow food too, but the land itself is about as poor as you can find for growing crops. The reason is because the mountainous parts of Southeast Asia are mainly covered in thick tropical rainforest and you might think well that's great plenty of rain and nutrient dense ground. This actually couldn't be further from the truth though. Tropical rainforests actually have some of the poorest arable land in the whole world, and the reason comes down to where the nutrients physically sit. In a tropical rainforest, around 80% of all nutrients in the entire ecosystem are locked up in the wood of the standing trees themselves, and only about 15% sits in the soil and leaf litter beneath them, and without nutrient-dense soil, you're going to struggle growing food at scale And clearing that jungle in the first place with nothing but hand tools a thousand years ago was a brutal amount of labour on its own. But even once it was cleared, the ground only stayed fertile for two or three growing seasons before the soil gave out completely, forcing farmers to abandon it and clear a fresh patch elsewhere and then wait years, sometimes a decade or more, for the jungle to grow back before they could do it all again. And in fact, agriculturalists are running into the exact same problem in the Amazon today. Clearing the land to grow crops only for the crops to die after a few years, forcing them to move further and further into the interior of the Amazon. Compare this to the Indo-Gangetic plain of India, where the Himalayas own rivers dump fresh mineral-rich silt onto the ground every single flood season. Scientists studying the tropics put a number on just how bad this trade-off is. Only about 20% of all land in the humid tropics has soil capable of supporting real agriculture at all. And virtually all of that fraction is already being used up, so the jungle separating one river valley from the next couldn't have supported the kind of dense, tax-paying population an empire needs to survive, even if someone had tried to clear it, which meant there was no economic reason to bridge the gap, on top of the mountains already making it physically hard. And the third reason isn't separate from the first two reasons at all. It's the same mountainous forested terrain but this time doing a different job and that job is disease or more specifically malaria. Warm humid climate and dense forest cover create exactly the shaded standing water conditions the Anopheles mosquito needs to breed and that combination is strongest precisely in uncleared forest and mountainous terrain not in cleared agricultural lowlands. Population-dense river valleys with farmland tend to have it mostly under control. It's the exact same terrain the three mountain ranges we've just covered where it persists. And malaria in this region repeatedly wiped out entire armies campaigning through it. In the Sino-Burmese Wars of the 1760s, the Anglo-Burmese Wars of the 1820s, and again in the Second World War. Even Chinese records from centuries earlier blame a disease they called miasma for repeatedly weakening armies sent south toward Vietnam. This was a genuine part of the buffer that kept Chinese expansion from ever fully absorbing the region into its enormous sphere of influence. So even a power big enough to try, the one regional player with the skill to potentially pull off what the Mauryas or Guptas did in India, ran straight into the same walls that everyone else did, mountains, poor soil and now disease, all sitting in exactly the same Same stretch of ground. So that brings us to the end of this video, I really hope you enjoyed it and obviously don't forget to subscribe if you don't want to miss any of my future uploads. So, I'll see you in the next one.