King Xerxes was killed in 465 BC, maybe by his son Ardashir I (Artaxerxes in Greek), who succeeded him. Ardashir was a weak king, and a lot of the conquered countries revolted while Ardashir was king. It took him a long time to reconquer them.
Ardashir, on a coin, with a Zoroastrian fire altar on the back, and his tomb.
Egypt revolted (with the help of Athenian mercenaries), and it took years of fighting before the Persians got control again about 455 BC. The island of Cyprus also revolted, again with the help of the Athenian navy. This time the Athenians won their battle, but the treaty between Cyprus and Persia ended up being a good deal for the Persians. Ardashir did manage to stay on good terms with the Jews, by letting them practice their religion, as Ezra and Nehemiah say in the Bible. Ardashir died in 425 BC.
A Persian princess (Persepolis)
(There are no pictures of Parysatis)
After Ardashir died, his son Darius II became King of Persia. He was the son of a woman Ardashir wasn't married to, and some people held this against him. Like his father, Darius II was a weak king; his half-sister, Parysatis, held a lot of the power. Darius and Parysatis, like Xerxes, too, spent most of their time trying to control revolts. There were revolts in Syria, Lydia, and Media (modern Iran). Egypt revolted again in 410 BC, and this time succeeded in breaking free of Persian control. However, as Greece got weaker during the Peloponnesian War, Darius II did manage to get more influence there.
Ardashir II of Persia (on a coin)
When Darius II died in 404 BC (just as the Peloponnesian War was ending), his son Ardashir II became King of Persia. But his mother Parysatis wanted to keep the power she was used to. She sponsored Ardashir's younger brother, Cyrus (who was still a teenager) to be king. Parysatis got together a bunch of Greek mercenaries (under the general Xenophon) and tried to kill Ardashir and make Cyrus king (which would have put Parysatis in power). When the troops met in battle, Cyrus' troops (the Greek ones) won, but Cyrus himself was killed in the battle, so Ardashir II went on being king anyway.
Ardashir II was another weak king like his father and grandfather, and never had much power himself. His mother Parysatis held a lot of power despite her treachery, and his wife Stateira was her main rival for power. About 400 BC, Parysatis had Stateira killed, and then she ruled on her own until her death.
When Ardashir II died in 358 BC, Artaxerxes III (his son with Stateira) killed off most of his brother's family in order to become the King of Persia. Ardashir III was a stronger king than his ancestors had been, and managed to reconquer Egypt in 342 BC. In other places, too, he stopped revolts and made Persia more powerful. But he was poisoned by one of his advisors, Bagoas, in 338 BC.
Bagoas put Ardashir III's son Arses on the throne, because Arses was a child and Bagoas figured he could tell Arses what to do. But when Arses began to grow up, Bagoas poisoned him, too, and in 336 Bagoas made Arses' cousin Darius III the King of Persia. He is probably the Darius mentioned in the Bible (Nehemiah 12.22). Bagoas put him on the throne thinking he would be easy to push around.
This is the desert where Darius III was killed.
Darius had a reputation for not being very ambitious. But then Darius fooled him - he murdered Bagoas. But having been picked because he was weak, Darius III did not make a very good king. When Alexander the Great invaded Persia, Darius was defeated in the battle of Issus (333 B.C.) and again in the battle of Gaugamela near Arbela (331 B.C.). In the end, Darius III was killed by one of his satraps, Bessus, in Bactria (modern Afghanistan), and Alexander took over the Persian Empire.
To find out more about the Persians, check out these books from Amazon.com or from your library:
The Persian Empire, by Karen Zeinert (1996). For kids. There are some errors, but basically a good introduction.
Ancient Persia, by Don Nardo (2003). For kids, good for reports.
Ancient Persia, by Josef Wiesehofer (2001). Includes the Parthians and the Sassanians.
History of the Persian Empire, by A.T. Olmstead (1948). An old book, but classic.
Ancient Near Eastern History and Culture, by William H. Stiebing (2002). Expensive, and hard to read, but it's a good up to date account.