Thread by @KhangXVu

Wanna hear a story about how Vietnam's geography shapes its national and state building for the past 4,000 years? Pay attention to the mountain range and the surrounding areas circled in red.

The Viet people originated in the Red River Delta in modern day Hanoi around 2,000 BC. As the population grew, they tried to find a way to expand the country.

They didn't have many options. The North is China, the East is the ocean, the west is the mountain. The South became the only route. This gave rise to the "march to the south" 南進 campaign that last for almost 1,000 years.

But wait, there is another problem. The mountain range in the west runs along the course of the route, which narrowed the width. It only took one horizontal mountain range to block the march. And yes, that exactly what happened.

Even before the march south, different Vietnamese dynasties, both under and independent of Chinese occupations, stopped somewhere in the middle because of those mountain ranges.

For example, the Han, the Wu, Tang, and Ming Dynasties

Vietnamese kings fought against Champa, who lived just north of the mountain range for hundreds of year. The geography often turned the military conquests into stalemates.

However, the stalemate was finally broken via a political marriage between a Vietnamese princess and a Champa king, which led the King to yield the mountain range and the surrounding areas to Vietnam in 1306. The princess Huyen Tran is now still revered for her sacrifice.

When Vietnam overcame the geographic stalemate, it quickly attacked and annexed the majority of Champa. Champa was too weak to pose a threat at this point. (Map from 1471 - Vietnam is yellow, Champa is light blue).

The annexation of Champa in mere several hundred years was remarkable considering the fact that Vietnam was stuck at that point for almost 2,000 years before.

The territory stayed the same for several hundred years. However, the Vietnamese imperial court was later split into two major factions (Trinh-Nguyen lords) with the territory being de facto split at where the march south began. (Map from 1653, Trinh is yellow, Nguyen is orange.)

There were thus two Vietnamese states, locked in a state of perpetual conflict for more than a century (1627-1775). Geographical factors that impeded the march south reinforced the existences of two different states. The two states used a river to demarcate the border.

That river somehow is close to the later DMZ during the Vietnam War (112 km apart to be exact).

The Nguyen lords won the war (this is a long story for another time) and reunified the country into the modern S-Shape.

Those horizontal mountains not only impact the courses of wars but also Vietnam's climate and social life. See how the mountains split Vietnam's climate?

The social life is also different. The Mekong Delta is 3 times the size of Red River Delta with no mountain ranges in the West.

Houses were thus spaced out. This is different in the Red River Delta, where houses were crammed in a smaller space. Population density in the North was three times that of the South.
North South

This made N. Vietnamese villages to be more close-knit than South Vietnamese ones. In wartime, that meant it was harder for spies to penetrate the North than the South. A former S. Vietnamese spy admitted the North successfully captured many spies. bbc.com/vietnamese/vie…

The essence of the Strategic Hamlet program was to build a tighter community to root out spies, something the North did not have to bother with because Northern villages were already tight. Resistance movements in the South proliferated while in the North they could not.

So yeah in the end, geography matters, and it all boils down to that mountain range at the beginning. It is Hai Van Pass located near Danang.