The best source of information about crucifixions comes from the four Gospels. But another valuable source of information about the practice of crucifixion is ancient Greek and Roman literature. The Greeks and Romans did not write about crucifixion a lot but, they wrote about it often enough to give important information about this method of execution.
The Romans didn’t invent crucifixion as a method of execution, though many believe they perfected it. The Persians were the first to use crucifixion. Ancient writings tell about King Darius having 3000 Babylonians crucified in about 519 B.C. Two centuries later, Alexander the Great also used crucifixion when he conquered different countries. Curtius Rufus said in History of Alexander that Alexander had 2000 citizens of the city of Tyre crucified after he conquered it. Execution by crucifixion became common under the rule of Alexander the Great (356-323 B.C.). The Romans conquered the Greeks and that is where they probably learned about crucifixion. Crucifixion was also used by many barbarian people, such as Indians, the Assyrians, the Scythians, and the Celts. It was also later used by the Germans and the Britains.
The Roman form of crucifixion was not used in the Old Testament by the Jewish people. In fact, it’s contrary to Jewish laws that require a person hung on a tree to be buried the same day. Romans, however, had no respect for such laws when it came to matters of the state. Jewish victims of crucifixion were hung for as long as anyone else. Shame was as much a part of the point as death. Jews saw crucifixion as one of the most horrible, cursed forms of death (Deuteronomy 21:23). The only exception I found reported was by the historian, Josephus when the Jewish high priest Alexander Jannaeus (103-76 B.C.) ordered the crucifixion of 800 enemy Pharisees.
In New Testament Bible times, the Romans used this tortuous method of execution as a means of exerting authority and control over the people. Roman authorities used mass crucifixions in order to subdue rebellious populations, especially in the difficult province of Judaea. Though Roman law usually spared Roman citizens from being crucified, they used crucifixion for rebellious foreigners, military enemies, violent criminals, robbers, and slaves. Sadly, slaves were so routinely crucified that crucifixion become known as the "slaves' punishment." When the slave rebellion of Spartacus was crushed, the Roman general Crassus had six thousand of the slave prisoners crucified along a stretch of the Appian Way, the main road leading into Rome. As for crucifying rebellious foreigners, Josephus tells about when the Romans were besieging Jerusalem in 70 A.D., the Roman general Titus, crucified five hundred or more Jews a day. So many Jews were crucified outside of the walls that "there was not enough room for the crosses and not enough crosses for the bodies" (Wars of the Jews 5:11.1).
Josephus wrote about Titus’ treatment of the Jews: