After the Median and the Neo-Babylonian Empire took over the Neo-Assyrian Empire (Coming Soon!), these 2 empires were really powerful. But the leader of Medes around 553, Astyages (585 - 550 BCE), was a tyrant- he was very cruel to his people. But the Median Empire was very strong! It stretched from Turkey to India. Nevertheless, a man called Cyrus the Great took his throne. Here is that story.
One day, the King of Medes had a terrible dream. He dreamt that his daughter, Mandane, gave birth to a child that would destroy his entire empire. He immediately married her off to Cambyses I, vassal of Astyages. Cambyses I was quiet and was a gentleman, so Astyages thought that he (and Mandane's) son would be like his father. But another dream was like the first one. Astyages was beginning to get worried. So he told a man called Harpagus to kill Cyrus, the son of his daughter (It is not clear if Cyrus is really the grandson of Astyages, though.) Harpagus was unwilling to do so, and instead, gave Cyrus to a shepherd, Mithridates, whose wife had a stillborn child. Then, Cyrus took the stillborn child to Astyages, and claimed that he had killed Cyrus. However, the real Cyrus was still in the hands of Mithridates. Then, Cyrus went back to his father. But Astyages discovered him! He threatened to kill Harpagus and his entire family for lying. But Harpagus escaped.
Many years later, around 553 BCE, Cyrus launched a rebellion against Astyages. And though his father Cambyses I died in 551 BCE, the rebellion succeeded in 550 BCE.
Then, Cyrus conquered Lydia (Modern Turkey). The King, Croesus, was the richest man in the world. His troops were very good, so some battles ended in a stalemate. Despite this, Cyrus the Great was victorious. But he wasn't done conquering yet. He attacked the Neo-Babylonian Empire, and again, he won. After conquering some tribes and minor kingdoms, he died in . He was succeeded by his son Cambyses II, who triumphed over Egypt, Kyrgyzstan, Sudan, Cyprus, South Sudan, made an attack into Ethiopia, and possibly even Somalia. After his brother and he got into a conflict, both of them died, and they were replaced by one of Cyrus' distant relatives, Darius the Great. Darius further expanded the Empire. But then it was followed by a defeat with the much smaller Greek army. (The Greek messenger, Pheidippides, sent the good news from Marathon to the Capital, Athens, and died from exhaustion; the Marathon race is named after this.) His successor, Xerxes I, tried again. After relative success, in which even Athens was sacked, Xerexes was defeated at a land battle in Plataea, and a sea battle at Salamis. Xerxes went to the center of his empire because he realized that he was in the middle of nowhere, while his general fought hard to keep the borders safe. However, he was defeated, and lost Greece, plus a few more countries. A man called Herodotus, on the Greek side, described these famous events.
Most people didn't rebel; The Achaemenid kings were good rulers. Cyrus even allowed the Jews (Israelites) to rebuild their temple. They also had a government with Satraps; the king did not have to keep control over his entire empire because the Satraps managed the regions. This helped it to last for more than 200 years as there were not many squabbles.
Every official had to bring a gift to the king every new year festival, and also had to pay their taxes. Though this might sound harsh, it isn't; the people were very rich.
Here is a list of what countries each king conquered.
Slowly, the Achaemenids began to grow weaker. Within 220 years of its founding it was devoured.