Prologue

When people first began to live on Earth, terrain was very different from what it is today. For tens of thousands of years, what we know as the country of Vietnam was the mountainous western edge of a broad plain. Now covered by the Gulf of Tonkin and the South China Sea, this plain extended in places for hundreds of kilometers east of the modern coastline and included a massif that we now call Hainan Island. Today we can imagine that beneath the mud at the bottom of the sea lie the relics of the people who inhabited this plain. But our knowledge of their existence comes only from the remains of quarries and workshops where they crafted stone tools at the tops of mountains along the modern Vietnamese coast. During that time, people also inhabited the mountains in what is now northern Vietnam, and we know of them from what they left in the caves where they lived.

About twelve to eight thousand years ago, the coastline shifted westward as sea levels rose with the melting of the ice-age glaciers. The water reached to around 5.8 meters above the modern level of the sea and penetrated into the mountain valleys. Thereafter, the sea gradually receded to its present level, exposing a chain of coastal plains that became the lowlands of what is now Vietnam. The most important of these plains for early Vietnamese history is the most northern of them. This is the plain of the Red River. It was formed by grey oceanic sediment emerging from the receding sea that has been increasingly streaked by accumulations of the red silt that has given the Red River its name.