Luke tells us in Acts 12:3 that Herod (Agrippa I) executed James, the son of Zebedee, with a sword. The problem is Luke never tells us why. He simply records the event. So, what prompted Herod to lift up his hand against certain disciples? Can we know? I don’t think it is possible to know with certainty, but I do believe we can come close to the truth by interpreting wisely some of what we find in Luke’s record.
It seems obvious from the method of execution that James was slain for political purposes. We know this, because execution with the sword, beheading, was a more honorable death than stoning and other such methods, which were reserved for criminals. The Romans also differentiated between methods of execution. Crucifixion was never used against a Roman citizen unless his crime was particularly barbarous or as a traitor. Tradition tells us that Paul, a Roman citizen, was beheaded, while Peter was crucified during the Nero persecution of the 60s CE.
At the time of James’ death, the Jews were particularly resentful and suspicious of Rome, due to the events of 39-41 CE when Caligula made an effort to introduce emperor worship in Judea by placing his image in the Temple at Jerusalem. The Jews and Rome were at the brink of war, and it was only through the diplomatic efforts of Petronius, the Roman legate and President of the Syrian Province, that war was averted.
After Claudius became Emperor in 41 CE, largely through a speech Agrippa made on his behalf before the Roman Senate, he made Agrippa king over Judea and all the territories of his grandfather, Herod the Great. This was done partially out of gratitude for his efforts to have the senate approve Claudius as Emperor of Rome and partially to insure the ‘Pax Romana’ in the East. Roman and Jewish relations had become strained and Agrippa’s appointment as king was expected to relieve those tensions.
Knowing this helps us understand what was to be Agrippa’s first order of business after taking over the government in Judea. He removed Theophilus, son of Annas, from the high priesthood and appointed Simon Kantheras, who was a descendant of the Boethus family. Herod the Great had given the high priesthood to Simon, son of Boethus, which was a powerful family in Alexandria, Egypt, and in doing so married his daughter Clopatria. From this union, Philip, the tetrarch of Ituraea and Trachonitis (Luke 3:1) was born. The Boethus family was very powerful in the high priest aristocracy in Jerusalem. The problem was, so was the family of Annas (the first high priest appointed by Rome in 6 CE), whom Agrippa replaced with that of Boethus.
Some believe Kantheras is a strong Grecized form of Caiaphas, implying that both of the most powerful high priestly families of Jerusalem were united, or at least attempts were made to ease the political tensions between them. In any case, Agrippa seems to have been governing on political eggshells. We come to understand just how powerful the Annas family was when Agrippa decided to replace Simon Kantheras with a member of the Annas clan. At first he offered the high priesthood to Jonathan, son of Annas, who held that office just prior to his brother Theophilus. In fact, it was most likely Jonathan to whom Paul had gone for “letters” to extradite believing Hellenist Jews from Damascus (Acts 9:1-2).
Nevertheless, Jonathan refused the offer of the king. Instead he suggested that the king give the office to his younger brother, Matthias! One has to step back at this point and take this in. The king was obviously making a concession to someone, whether to Rome or to the Annas family, by removing the favorite high priestly clan of the Herodian dynasty and offering that office to Jonathan. Yet, not only did Jonathan refuse the king but thought it his place to advise Agrippa concerning whom he should make high priest (!) and the king condescended and took Jonathan’s advice! One must ask—who is in control here?
So, this is the political climate under which James, John’s brother, was executed. He was slain as a political enemy, but of whom? The Roman government at this time had considered the Jesus Movement politically innocuous. This being true, why did Herod consider James his enemy? We get an implication from Acts 12:3 that he did it in an effort to please the Jews—that is, those in authority, meaning the Annas family. Agrippa sought to govern his kingdom by taking advantage of the good graces of those who had the greatest power. If he offended the powerful in his kingdom, his own efforts at governing would be less effective. So, he slew James. If we consider the text closely, we get the impression that Agrippa was unsure that killing James would bring the desired result, but when he saw it did (Acts 12:3), he then seized Peter, intending to kill him after the Passover.
Luke tells us that Peter escaped, and Herod must have considered this a bad omen, because he immediately replaced Matthias with Elioenai, the son of Kantheras, and a descendent of the Boethus clan. Seeking to enhance one’s condition through political means is to build one’s future upon the shifting sands.
 This Herod Philip is not to be confused with the Philip, also Herod’s son, and husband of Herodias, whom Herod Antipas, the tetrarch of Galilee, had taken as his wife (Mark 6:17). The former was a ruler, while the later was not.