Perhaps the adjective "greatest" is something of hollow praise for the men on this list. After all, the defining characteristic of conquerors is the ability to kill others and take their stuff; moreover, to convince people underneath you to kill people and take their stuff. Most all of these men were great strategists, with varying levels of intellect. In some trains of logic, the blood of all those who died in the wake of their armies is entirely on their hands. Somehow, that thought didn't stop them from gobbling up the land of their enemies as their empires expanded.
All of the men on these lists have had a great and terrible influence on human history. In one sense, these are the most influential people in history, in the purest sense of the word "influence". Multi-continental war, genocide, death and destruction are some of the tools of their influence; their legacy. History shall always remember them as warmongers, for better or worse.
Truthfully, the everyman judges these men not on exactly how many they killed or how much they conquered, but their motive. For the sake of this list, we measure their greatness as conquerors by the amount of square miles they conquered. Most people probably couldn't even guess the #1 conqueror, let alone consider him hated. Recent history is always more pertinent to our lives, even if it is just as dead and gone as history from thousands of years ago. Adolf Hitler graces (or sullies, rather) this list, and is easily the most hated dictator in history, but he's far from the most influential. He did after all, suffer arguably the greatest downfall of any on this list.
10 George W. Bush -- 423,424 Square Miles
Number ten on the list is quite fresh in the mind of history. During George W. Bush's eight-year, two-term presidency of the U.S.A, the "war on terror" was waged on real land, regardless of how ephemeral of a title it suggested. In retaliation to the September 11th attacks on American soil-- the first of its kind since Pearl Harbor-- the American Military mobilized en masse to extricate Saddam Hussein from power in Iraq, though the link of him to nuclear weaponry or the 9/11 attacks was tenuous at best. Even though the extrication of Hussein was a boon, the war raged through the country before he was ever found. From there, the war spread across the middle east in an effort to eradicate terrorist cells and eliminate Taliban and Al Qaeda presences. It's been nearly 13 years since the war on terror, or more accurately, the war in the middle east, began, and it's become quite the quagmire over that time. Incredibly, so much ground has been covered during the invasions that George Bush lands at 10 as one of the greatest conquerors in history.
9 Francisco Pizarro -- 480,000 Square Miles
This Spanish Conquistador lived from 1471-1541, and was the leader of several expeditions to South America where he would go on to conquer numerous parts of the continent, famously conquering much of the Incan empire. Pizarro was inspired to conquer South America, along with other Spanish "explorers", by the successes of Hernan Cortes' exploits, including the vast treasures he acquired. Pizarro first unsuccessfully attacked the western coast of South America, but on his third expedition he landed in what is now Ecuador, and drove to the Incan capital of Tumbes, only to find it ruined by Incan civil war. He eventually fortuitously came across the unprepared Incan Emperor Atahualpa and captured him, after he had defeated his brother in the Incan civil war. The Emperor would later be executed, and Pizarro basically defeated an entire nation with only horses and 160 technologically advanced (at the time) soldiers. He later had four children with two Incan princesses, and had conquered what is modern day Peru. He's remembered in Peru as a sort of confusing figure, as he historically influenced the nation but was also unquestionably a brutal conqueror.
8 Mahmud of Ghazni -- 680,000 Square Miles
Mahmud of Ghazni lived from 971-1030 A.D., was the first Sultan in history, and is credited as the founder of the Ghaznavid empire. Sultan had come to mean that he was the ruler of a great expanse of land that covered much of the middle east, in what is now Iran, Afghanistan, Pakistan, and some of India, along with a number of smaller countries. His conquests are largely attributed to the use of extremely powerful archers on horseback, using compound bows atop horses to speed across the battlefield and kill from great distance. Mahmud is possibly one of the best conquerors on this list, for despite his conquests he treasured learning, regularly bestowed honor onto wise and well read men, and created universities and mosques across the middle east and Asia. Though much of his wartime policy involved the death of infidels, or all those who did not believed the sect of Muslim that he did, he often tolerated religious groups so long as they didn't pose a military threat to him. The Mahmud of Ghanzi is undoubtedly a conqueror that fits more into the grey areas of despotism, as he in many ways showed a temperate and learned disposition while ruling his empire.
7 Napoleon Bonaparte -- 720,000 Square Miles
One of the more famous conquerors in history, Napoleon was a brilliant strategist and war general who quickly rose to the top of the military school he was raised in. Not only did he bring France military greatness and rose to Emperorship for 10 years from 1804-1814, he also created the reform that abolished feudalism and allowed widespread religious toleration. He also created a legal code for his people called the Napoleonic Code which served as a major influence in creation and adjustment of law worldwide. Napoleon led the French army to conquer most of continental Europe, his only blunder was invading Russia which would eventually lead to his downfall and exile before his eventual death on the island of Elba. Without a doubt he is the most positive conqueror on this list, as he espoused many of the French revolutionary ideas that helped shape much of democracy as we know it today.
6 Adolf Hitler -- 1,370,000 Square Miles
Adolf Hitler doesn't need much introduction. If you're someone who has access to the internet, then you surely know the horrific history of one Adolf Hitler whose very name instills thoughts of hatred, bigotry, violence and death. He may only be #6 on this list, but he is easily the most hated conqueror in today's worldview. The economic gutting of Germany after World War I is often attributed to be the cause of World War II, as it allowed the Nazi party to rise in power simply by providing food and jobs for the German people. But the mastermind, the unquestioned leader who created the Axis that sparked WWII, was Hitler.
Figures vary as the full scope of the war was nearly impossible to ascertain, with events like Japanese massacres in China being hard to historically quantify, but it is generally accepted that more than 55,000,000 people died in World War II. In many ways, its entirety can be lain at the feet of Hitler himself. Hitler's demands for purification of race and global domination through war might not be original, but the scope of which they were executed remains the most horrifying periods in human history. Of the 55 million, over 29 million were civilian deaths, notably the 6 million Jews and other "racially impure" people killed by Hitler's genocide. We can only hope that this is the the darkest stain in human history, and will one day be looked at as a distant history lesson.
5 Attila the Hun -- 1,450,000 Square Miles
Attila The Hun, also known as Flagellum Dei, or "Scourge of God" is one of the greatest barbarian conquerors in all of history. The Scourge of God title was bestowed upon him because of the rampant destruction he rained down on the Roman Empire, he led the Huns, an eastern European barbarian tribe, to conquer much of eastern and central Europe. His birth date is unknown, but he reigned between 434-453 A.D., where he controlled an empire from Italy to Germany, Russia, Poland, and southeastern Europe. While he never was able to successfully conquer Persia and Constantinople, he repeatedly invaded the Roman Empire, and was renowned for the devastation and plundering he left in the wake of his barbarian hordes. Attila dominated Europe during his reign, until the Visigoths and the Romans actually joined forces to defeat the conqueror. He died in 453 A.D., and with no established order to follow him, the barbarian empire crumbled soon thereafter.
4 Cyrus The Great -- 2,090,000 Square Miles
Often described as the founder of the Persian Empire, Cyrus the great reigned from 559-530 B.C. Persia was originally a state within the empire of Medes, until Cyrus liberated Persia, started a revolution and took the Median capital of Ecbatana, and proclaimed himself ruler. His Persian Empire was gigantic, as he conquered from India to the middle east, northern Africa and into Greece. His conquests led to the Persian Empire as being one of the largest and most historically influential empires in recorded history. Unlike Attila, Cyrus created a political infrastructure under him that kept the Persian Empire going long after his death, and his exploits as a conqueror lead to the spread of middle eastern philosophy, literature, culture and religion across Europe and Asia. Persia remained in existence for a long, long time and is often attributed to the spread of Islam and the Islamic "Golden Age".
3 Tamerlane -- 2,145,000 Square Miles
Timur, Tarmashirin Khan, or more commonly known in history as Tamerlane, is the second greatest Asian conqueror who founded the Timurid dynasty. A figure of Islamic faith, he often called himself "the sword of Islam" and used religious rhetoric and aspirations to recreate Genghis Khan's Empire as a motive to drive his multicultural army all across Asia, Africa and Europe. Incredibly, his vast expanses of military conquest is estimated to have caused 17 million deaths during his reign from 1370-1405. That is also thought to be about 5% of the population of the world at that time. So it may not surprise you to know that Tamerlane is known most prominently as a military figure and for his violent conquests across the world, rather than his Muslim influences and his love for art and architecture. Because of his religious motivations though, his existence and subsequent empire is the main reason why Christianity was largely expunged from Asia, and conversely why the Muslim cultural world flourished.
2 Alexander The Great -- 2,180,000 Square Miles
Easily one the greatest conqueror in western history, Alexander the great created an empire so vast for its time it is staggering. He succeeded his father, Philip II, when he was 20 years old, having been trained in warfare and tutored by Aristotle. He took command of the Macedonian Empire and ceaselessly spread from Greece eastward. He defeated the Persians, conquered Egypt and tore through Asia Minor all the way to India where he finally stopped his conquest at the behest of his soldiers. His influence spread across the world, creating around twenty cities named after him, the most famous being Alexandria in Egypt. His empire also created trade between the east and the west, though that was something of an unintended consequence, historically speaking. He also greatly influenced Rome and Roman thinking in the military, as Romans often looked to Alexander and his tactics for military knowledge. In fact, his military brilliance was so extensive that military academies around the world still teach tactics he created to this day. After his death in 323 B.C. his empire split into a number of parts, as territories and rulers squabbled over rights to rule. Despite the fall of the Macedonian empire, his influence on the world would greatly change the course of human history.
1 Genghis Khan -- 4,860,000 Square Miles
Without a doubt, the greatest conqueror in history, who conquered more than double the area of land that Alexander the Great did, is often one of the most forgotten conquerors in the minds of people of the western world. Genghis Khan (birth name of Temujin) is often reduced to a caricature, a cartoonish idea of a big barbaric Mongol who terrorizes villages. Well, he certainly did terrorize plenty of villages over his lifetime. He was born in 1162 in Mongolia, and created his empire first by unifying nomadic tribes of northeast Asia into one army, where he would sweep across Asia and western Europe with unprecedented speed and efficiency. He conquered what is nearly the entirety of modern day China, as well as spilling over into Russia, Turkey, most of the Persian middle East, and nearly everything in between (except India). The scope of his conquests are so enormous that it seems nearly impossible for anyone at the time, with only the speed of horseback to have created such a massive empire as that of the Mongol Empire. Though he is often credited with creating the unified concept of the Silk Road from Asia to Europe, that's about the extent of the positive depictions of Genghis Khan, as he is responsible for the deaths and conquest of innumerable peoples across the known world. However he is remembered, since his death in 1227 A.D., he remains the single greatest conqueror in human history by a incredibly wide margin.