Throughout the world's history, conquerors have taken over new lands and built empires. Their influence often lives on long past their deaths and can transform the course of history.

Over the history of the world, lands have changed hands many times. Often, the world's most significant changes result when a powerful leader emerges. Once the leader has assembled an army, they take over the land around them through the use of or the threat of mass violence and begin to form an empire. The leader's descendants may continue to gather territory or lose control, giving up the lands to a new empire builder.

Conquerors, though, can continue to transform places long after they have died. A few examples from ancient history show the powerful effects of different conquerors on the world.

Alexander

Alexander—sometimes called Alexandria the Great—was born in 356 B.C.E. to King Philip II of Macedonia. After his father's death, he became king at age 20. Alexander quickly set about expanding his kingdom, applying both his military ability and political skills. By the time he died at age 32, Alexander had conquered a huge empire that extended from Macedonia to Egypt and from Greece to part of India. He ruled over the largest empire in the ancient world.

Alexander was keen to learn everything he could. He enlisted scientists to travel with the army. They recorded information about the plants, animals, and geography of his new territories. Alexander encouraged his people to live among and marry the people they conquered as part of his goal of a unified empire. He also founded cities, often named Alexandria, as centers of Greek government and learning. The most famous city was Alexandria, Egypt, which would continue as a center of learning long after his death and is still a thriving city of millions today.

Alexander the Great's conquests spread Greek culture, language and ideas throughout Asia Minor (made mostly of modern-day Turkey), Egypt, and India. Greek culture became entwined with local cultures. The changes were so significant that historians have named the time period the Hellenistic Age or Period. The Hellenistic Period began after the death of Alexander in 323 B.C.E.

Hellenistic culture grew and evolved in the kingdoms that followed Alexander's death. Elaborate works of art and libraries were built, and philosophers and scientists contributed to academic advances. The Hellenistic Period came to an end when Roman troops captured the last of Alexander's territories at the Battle of Actium in 31 B.C.E.

The Norman Conquest

In 1066, King Edward of England died without an heir, and his brother-in-law Harold assumed the throne. William, the duke of Normandy in France, believed he had a better claim to the title of king than Harold. He gathered an army and launched an attack on England. Harold was killed at the Battle of Hastings, and William was crowned the new king, ending 600 years of Anglo-Saxon rule. Today, this event is remembered as the Norman Conquest.

The Norman Conquest had a dramatic effect on the political and social landscape of England. William kept careful records of the land and its resources in the Domesday Book so he could tax his subjects more effectively. He also took land from the English elite to give to Norman nobles who pledged their allegiance to him. This was known as the Norman system of feudalism and turned England into a powerful and well-organized feudal state. Finally, William formed the Great Council, a group of nobles and church leaders who helped him make decisions. The Great Council would eventually evolve into what is now known as the British Parliament.

The Norman Conquest also influenced culture and architecture. Protective castles were introduced to England. The Normans also built churches and soaring cathedrals more typical of continental Europe. The language changed, too, as French became the language most commonly used in legal and administrative circles. Even today, the motto on the British Coat of Arms is not in English but French.

The Mongol Empire

In 1206, the Mongol Empire emerged in Asia. At its peak in the 14th century, the Mongol Empire stretched from China to Eastern Europe, making it the largest connected empire in world history. Perhaps it is no surprise that these conquerors would change the history of the world.

Some of the effects of the Mongol conquests were felt for hundreds of years. They destroyed irrigation systems in present-day Iraq and Iran, ruining the area's agricultural system. The loss contributed to the instability of the region.

However, the most lasting impact of the Mongol Empire was the peace that resulted from Mongol rule. The Silk Roads, a network of trade routes extending across Asia and into Europe, were under Mongol control. Knowledge moved freely between the Far East, the Middle East, and Europe, contributing to advances in mathematics, medicine, and astronomy. Chinese inventions and ideas spread to Europe, and European goods and ideas flowed to Asia. Unfortunately, with these exchanges came the spread of diseases, which traveled along the Silk Road. Research suggests the Mongols carried the plague, known in history as the Black Death, bringing the illness from Asia to Europe. In Europe, the disease killed upwards of 25 million people.