During the eighteenth century, when the British were establishing their control over Indian, Many of the British administrators were also scholars trained in Greek and Latin. One of these scholars was studying Sanskrit, the language in which the Hindu sacred books are written. He became aware that Sanskrit seemed to be closely allied with both Latin and Greek. The Sanskrit word for "Great King," for instance, is maharaja, and the Latin term for the same thing is magnus rex. Some other words are even closer: "mother" in Sanskrit is mater, in Latin mater, in German Mutter, and in English mother. One could extend that list greatly, but the real tip-off that there was an actual relationship was that the grammar of Sanskrit on the one hand and Latin and Greek on the other hand were too similar to be accidental or the result of borrowing. Scholars were excited by this discovery and began studying other related languages, such as Iranian, Russian, all of the modern Western European tongues, and a number of dead languages. They found them all related and gave the name of Indo- European (from the fact that these languages spread from India all the way to Europe). They began to ask how this family of languages, of which their own was usually a member) had spread over such a vast expanse of territory.
It didn't take them long to realize that most of the Indo-European tongues for which some historical origin was known were spoken by, and often introduced by, chariot-driving peoples. It was only a short jump from this to trying to discover the place where these people had originated. There were various theories, much study and even more argument, but most scholars accepted the idea that the original home of the people speaking the original Indo-European language from which all of the other languages had descended was probably somewhere near to, and northwest of, the Caspian Sea. The scholars decided to call these ancient people Aryans, the name that the Indo-European-speaking invaders of India, and close to that of the conquerors of modern Iran (in which name that of these people is preserved). They pictured the Aryans as a people comprised of small tribes, ruled over by a warrior chieftain who was also their lawgiver and believed to be descended from one of the gods. One of the arguments used to support this view was the similarity of some words: the Latin rex, or "king"; the English word right (spelled in that funny way because it was originally pronounced something like "wrecked") in the sense of "law," "justice," and so forth; rita, the Sanskrit root with which English "rite," "ritual" and similar words connected with the practice of religion are derived; and the English rich, or "wealthy".
This society was thought of as being divided into relatively rigid classes: the warrior/wealthy/law-giving/and god-like nobles, the shamans who assisted them and who were, although not noble, distinguished by "magic" powers of prophecy and the like and were servants of the god of the tribe, and the mass of common people. Aryan society, being primarily nomadic, was dominated by the males and this was reflected in their religion. They worshipped the personified forces of nature, but, even before they began to expand, they must have recognized one supreme god, since the name of the father-sky-god are quite similar in all of the languages of the Indo-European family: Sanskrit Dyaus pitar, Greek Zeus pater ("Zeus" originally being pronounced something like "dzh-eh-oos"), and Latin Jupiter. When the Aryans conquered an agricultural society, they often accepted the local goddesses and paired them off with their own gods as husband and wife, such as Zeus and Hera, Hephaestus (god of the forge) and Aphrodite (goddess of sexual love), and so forth. In the Aryan society, and in the societies derived from it, the role and status of women -- since they could not be warriors except in myths like that of the Amazons -- was considerably diminished, and women were treated as inferior to men.
One could go on a great deal longer with this sort of thing, but you should recognize that all of this is really speculation and involves a great deal of reading the present back into the past. Archaeological work in Rumania over the past twenty years has uncovered settlements of peoples who were smelting bronze and using chariots long before the invasions of the chariot peoples began. Moreover, these early bronze-users were sedentary agriculturalists, and they appear to have expanded relatively peacefully into the peninsula of Europe. The scholars of the nineteenth century saw the Aryans as the original Europeans, and it suited that century of European imperialism to picture their ancestors as strong and dynamic, a conquering people, sweeping down in their war machines to establish their overlordship over the various "lesser" peoples of Europe, Asia, and even Africa. It was also an era in which the monarchs and aristocracy of Europe were trying to hold on to their power in the face of popular uprisings and revolutions, and it suited them that people should view the original European, or White, "Race" as having been subject to a powerful elite. Finally, of course, it was an era in which women in the more advanced Western countries were demanding basic rights and a fair share of political and economic power in a society to which they were contributing a great deal. The picture of early Aryan society, the historic foundation of European society and culture, as male- dominated was an argument against such demands. For all of these reasons, historians and archaeologists are now reacting against the traditional view of Aryan society and the conquests of the chariot peoples, and many are discarding the entire idea of an "Aryan people" as pure imagination and wishful thinking.
This may be carrying things a bit too far. There are some facts that cannot be simply dismissed. The chariot peoples did invade some countries, and, in those countries that they invaded, they did introduce a language that falls into the Indo-European linguistic family. Just as important, in some cases, they left behind a tradition that is reflected in ancient epic poems. These epics, such as Homer's Iliad and the massive Indian epics known as the Ramayanaand the Mahabharata, in the latter of which one finds the passage known as the Bhagavad gita, as well as some of the Hindu sacred texts, particularly the Vedic Hymns, reflect a society dominated by a warrior-elite, fighting from their chariots, and possessing personal values and attitudes that we normally associate with those of an Heroic Age. Unfortunately, too few such epics have endured to draw any firm conclusions from them as to the nature of the chariot-driving/Aryan/Indo-European-speaking peoples. The Kassites, Hyksos, Tocharians and others may each have had their own epic songs, comparable to the Iliad and Bhagavad Gita, but, if they did, their songs have not survived.
One would like to believe in the traditional view of the Aryan peoples and their conquests, if only because makes for a more coherent view of the history of that period: the early invaders of Mesopotamia learned elements of civilization, such as the pantheon of gods personifying natural forces, some elements of writing, and so forth, from the Babylonians and Sumerians, and that they shared it with other peoples of their sort. They then took this, together with their own culture and technology, and spread it among the peoples whom they subjugated. We can imagine that people had grown more and more differentiated during the long expansion, first of the species and then of agriculture, and that the Aryan conquests, as bloody and as oppressive as they may have been, restored to the peoples of the Eurasian continent a common cultural basis that would allow the exchange of ideas and values in the future.
But saying that it would be nice if a certain aspect of the past were true, doesn't make it so, does it?