In the sixth century B.C. there were sixteen major states and several smaller ones in the northern third of India. Some of these states were fully developed monarchies; others were republics made up of one or more tribes. The four strongest states - Kasi, Kosala, Magadha and Vrjji - were all along the Ganges River. Of those four, Magadha had several advantages that would help it to prevail in the struggle for supremacy.

Magadha formed one of the sixteen Mah?janapadas and had its capital at R?jagaha or Giribbaja where Bimbis?ra, and after him Aj?tasattu, reigned. Later, P?taliputta became the capital. By the time of Bimbis?ra, Anga, too, formed a part of Magadha, and he was known as king of Anga Magadha. But prior to that, these were two separate kingdoms, often at war with each other. Several kings of Magadha are mentioned by name in the J?takas - e.g., Arindama and Duyyodhana.

In the Buddha’s day, Magadha (inclusive of Anga) consisted of eighty thousand villages and had a circumference of some three hundred leagues. Aj?tasattu succeeded in annexing Kosala with the help of the Licchavis, and he succeeded also in bringing the confederation of the latter under his sway; preliminaries to this struggle are mentioned in the books.

At the time of the Buddha, the kingdom of Magadha was bounded on the east by the river Camp?, on the south by the Vindhy? Mountains, on the west by the river Sona, and on the north by the Ganges. The latter river formed the boundary between Magadha and the republican country of the Licchavis, and both the M?gadhas and the Licchavis evidently had equal rights over the river. When the Buddha visited Ves?li, Bimbis?ra made a road five leagues long, from R?jagaha to the river, and decorated it, and the Licchavis did the same on the other side. It is said that monks going from S?vatthi to R?jagaha could cross the Ganges in boats kept either by Aj?tasattu or by the Licchavis of Ves?li.

During the early Buddhist period Magadha was an important political and commercial centre, and was visited by people from all parts of Northern India in search of commerce and of learning. The kings of Magadha maintained friendly relations with their neighbours, Bimbis?ra and Pasenadi marrying each other’s sisters. Mention is made of an alliance between Pukkus?ti, king of Gandh?ra and Bimbis?ra. When Candappajjota of Ujjeni was suffering from jaundice, Bimbis?ra sent him his own personal physician, J?vaka.

In Magadha was the real birth of Buddhism, and it was from Magadha that it spread after the Third Council. The Buddha’s chief disciples, S?riputta and Moggall?na, came from Magadha. In Asoka’s time the income from the four gates of his capital of P?taliputta was four hundred thousand kah?panas daily, and in the Sabh?, or Council, he would daily receive another hundred thousand kah?panas. The cornfields of Magadha were rich and fertile, and each Magadha field was about one g?vuta in extent.

The names of several places in Magadha occur in the books - e.g., Ekan?l?, N?Iakag?ma, Sen?nig?ma, Kh?numata, Andhakavindha, Macala, M?tul?, Ambalatthik?, P?talig?ma, N?Iand? and S?Iindiya.
Buddhaghosa says that there are many fanciful explanations of the word Magadha. One such is that king Cetiya, when about to be swallowed up by the earth for having introduced lying into the world, was thus admonished by those standing round, another that those who were digging in the earth saw the king, and that he said to them: “ M? gadham karotha.” The real explanation, accepted by Buddhaghosa himself, seems to have been that the country was the residence of a tribe of khattiyas called Magadh?.

The Magadhabh?s? is regarded as the speech of the ?riyans. If children grow up without being taught any language, they will spontaneously use the Magadha language; it is spread all over Niraya, among lower animals, petas, humans and devas.

In 518 B.C. (or 513?) the Persian king Darius I advanced to the Indus River, annexing the kingdoms there. For over a century the Indus valley was the twentieth and easternmost satrapy (province) of the Persian Empire. The rest of India was unconquered, but the Indians learned the use of iron, coinage and writing from the Persians during this time. As the Persians grew weak in the fourth century, a local ruler named Porus declared independence (338? B.C.). The Persians were unable to regain control before Alexander the Great conquered their empire.

Pursuing his campaign to the farthest frontier of Persia, Alexander entered India in 327 B.C. After he got through Afghanistan, there was a pitched battle with King Porus on the banks of the Jhelum River, a tributary of the Indus. Porus had a huge force of infantry and cavalry, and 200 war elephants, to repel the invader. Instead of waiting for Porus to come to him, Alexander took the initiative, leading his army across the river under cover of a thunderstorm.

The battle was an awful slaughter for both sides, until the elephants panicked, trampling the Indians in their stampede. Porus surrendered, and Alexander asked him how he wanted to be treated. “Like a king,” Porus replied. In admiration of a gallant opponent, Alexander restored him to his throne and made him governor over his Indian provinces.

Alexander was curious about the land he had entered, with its strange animals, rubies and gold, steaming jungles and dusty plains, the farthest place known to the Western world. Beyond the Ganges--or so everybody believed--was the encircling ocean that marked the end of the world. Alexander was determined to wet his feet in it.

Chandragupta urged Alexander to go on, confident that the Macedonian army could attack and defeat Magadha.
The troops had other ideas. The battle with Porus was bad enough, and rumors came to them of even stronger armies awaiting them in the east. After marching 200 miles, they stopped and refused to go any farther. Alexander took to his tent. When he emerged three days later and announced they were going home, the troops rejoiced. “Alexander,” they said, “has allowed us, but no other, to defeat him.”