By the 1st millennia BC, the area that is now Northern Vietnam had already evolved a rice-based culture and it is imaginable that with the Red River dissecting the region and the sea in such close proximity, fish and seafood were also part of the diet.
In 208 BC the Chinese invaded the northern territory and dominated the culture for 1000 years. They introduced much of their culinary practices, such as noodle based dishes, stir-frying the use of chopsticks and woks. It's interesting to note however, that despite this long Chinese occupation, the Vietnamese always considered themselves as a distinct people, and on several occasions, fought to evict the Chinese. It wasn't until the mid 10th century AD that they managed to do so and restore Vietnamese independence but in all this time, their desire to hold on to their identity was reflected in their cuisine.
The Vietnamese empire spread to Angkor, later to become Cambodia, and by the 15th Century, both Vietnam and Thailand, sized territories from the disintegrating Angkor state. By 1700, all of the Mekong River Delta was in Vietnamese hands and had spread to to the region which was controlled by an Indianised trading state known as Champa. This is undoubtedly where the Vietnamese curry was born, albeit not as fiery as those found in other parts of India, but definitely curry.
In 1859, the French colonised Vietnam. They remained for 100 years and also had a profound influence on Vietnamese cooking, introducing, amongst other things, the technique of sautéing, the use of bones to make stock, the use of white potatoes and even the French baguette!
Neighbors have influenced the Vietnamese people in regards to what they eat and how they cook. People from Mongolia who invaded Vietnam from the north in the tenth century brought beef with them. This is how beef became part of the Vietnamese diet. Common Vietnamese beef dishes are pho bo (Beef...