The defeat at the Battle of Bull Run indicated to the union that the civil war was not going to be an easy "90 day war" like they initially thought it would be. The union realized that they had a real, serious war in front of them and they needed to prepare accordingly.
Answer:
African nationalism first emerged as a mass movement in the years after World War II as a result of wartime changes in the nature of colonial rule as well as social change in Africa itself. ... Rotberg, African nationalism would not have emerged without colonialism.
Posting again:
Historians work to methodically dissect the past to help us understand the present and avoid making similar mistakes in the future.
The base job of a Historian is to break down a historical events into parts to understand how the historical event or historical arc could have occurred as it did. This could range from "Why did the Japanese bomb Pearl Harbor" to "Why did the Union win the Civil War"
Each question has answers that can help future generations understand the implications of their actions.