What civilization worked on a flood cycle?

What led directly to the formation of the Mongol empire? Why was the wheel history's most important invention? What is cowherd? Abolitionists often opposed annexation of western territories because they? What country did the last name HILL originate from? What did West African kings became powerful by controlling this? Did the black knight ever really exist? Did Arthur Currie change the lives of Canadians? What was the role of a medieval slave? Where was the roman empire located in 753 BC? Why did a group known as theologians arise during the Roman Empire rather than the Roman Republic? What does GTW stand for? What do shoulder plates do for roman soldiers? How where the Germanic groups able to cross into Gaul in ad 406? What are the Explorations in chronological order? Which best explains why Europeans wanted the discover a direct trade route to Asia? What was the first organized civilization in history? In what time period did Norse culture originate and thrive and decline in? What is a millenery? Why was setting the nations western border was important economically to the new country?