Geography affects every aspect of history as it is responsible for determining the winners of wars, the prosperity of people and the formation of cultures. To quote the Bradley Commission on History in Schools, "...geography is by nature the constant companion of historical studies; it is hardly possible to grasp the one without the other." Because the events of history take place on the stage of the world, they are inevitably influenced and even determined by geography.
Rivers are an easy example of how geography can impact history. Most of the earliest human civilizations developed along large rivers because of the nutrients that were deposited in the surrounding soil during annual floods. Without the specific geography of India, Mesopotamia, China and Egypt, ancient farmers would have quickly used all the nutrients in the soil in these places, and that would have meant that the farmers would have had to keep moving to grow crops. That would have meant that they never would have settled down long enough to develop the advanced tools and societal structures associated with civilization. With rivers, however, these early people had an easy way of transporting goods and a natural defense against invaders in addition to a vital source of food.
The influence doesn't end there, however. Rivers allowed the Vikings to raid far into inland Europe, and the Mississippi River made it far easier for Europeans to explore North America. Moreover, other geographic features, such as mountains and plains, have had an equally strong impact on history, like when 300 Spartans used the mountain pass at Thermopylae to hold off thousands of Persian soldiers.