The Empires in the Middle Ages unit covers the history of both the Middle Ages in Europe and the Islamic Medieval Empires. The Middle Ages in Europe and Islamic Medieval Empires units have always been companions in the Grade 4 sequence because their subjects are highly related. While the Middle Ages deals primarily with the events of western Europe, and the relationship between the Christian Church and the rulers of the region, the concurrent Islamic Empires in the Middle Ages unit looks at events in another part of the world (particularly in what is now called the Middle East). Separated by the Mid-Unit Assessment, the two topics of study are tied by a common past (the decline of the Roman Empire) and intersecting events such as the Crusades and the movement of knowledge, philosophy, and science from Greek into Arabic into Latin. They are also tied by their impact on the present: it is difficult to understand the modern world without knowing about these two regions and their medieval history.