The Black Fortress
Machaerus (seen in the photo below), meaning the Black Fortress, was located on the frontier of Arabia, about 9 miles / 15 kilometers east of, and at an elevation 3,860 feet above, The Dead Sea (seen in the lower background of the photo). Originally built by The Maccabees, it was destroyed by Roman forces under Pompey, but thereafter the Romans, particularly in the time of Herod The Great (the Roman-appointed "king of Judea" who, while attempting to have the newborn Christ killed, ordered the prophesied (Matthew 2:17-18, Jeremiah 31:15) slaughter of many other infant Jews in and around Bethlehem i.e. Matthew 2:16-18) rebuilt and expanded the royal residence, military facility and prison. It was at Machaerus, according to the Jewish-Roman historian Flavius Josephus, who lived through much of the New Testament era, that the Biblically-recorded martyrdom of John The Baptist occurred in the time of Herod the Great's son, Herod Antipas (see the Fact Finder question below).
"And he sent, and beheaded John in the prison"
John was a fearless servant of God, that is to say, he feared only God. When Herod Antipas committed adultery (which according to Josephus, was adultery and incest), John boldly rebuked the tetrarch for his sin, just as he would have anyone else. Unfortunately, for John, this occurred at the time when John's service to God was very nearly complete; by definition (i.e. "to prepare the way"), John's ministry effectively ended when Jesus' ministry began (to understand this, and other examples, of someone preparing the way for someone else, see "Land On Which You Had Not Labored").
The Scriptures below, perhaps surprisingly, indicate that John, even at that late time, and despite earlier signs, was not yet fully certain of the identity of The Messiah that he was preparing the way for, even though he was absolutely certain that he was preparing the way for the Messiah (this is not unprecedented; there are numerous examples in the Bible of God's servants given only what they need to know, when they need to know it e.g. "And I appeared unto Abraham, unto Isaac, and unto Jacob, by the Name of God Almighty [i.e. El Shaddai, see El], but by My Name Jehovah [see YHVH, Adonai, Jehovah, LORD] was I not known to them." Exodus 6:3 KJV), but on the other hand there was most definitely no doubt in Jesus' mind that John was indeed the "Elijah to come" for that time (see The Elijahs). Jesus had a very high regard for John:
"And it came to pass, when Jesus had made an end of commanding His twelve disciples, He departed thence to teach and to preach in their cities."
"Now when John had heard in the prison the works of Christ, he sent two of his disciples, And said unto Him, Art Thou He that should come, or do we look for another?"
"Jesus answered and said unto them, Go and show John again those things which ye do hear and see: The blind receive their sight, and the lame walk, the lepers are cleansed, and the deaf hear, the dead are raised up, and the poor have the gospel preached to them. And blessed is he, whosoever shall not be offended in Me."
"And as they departed, Jesus began to say unto the multitudes concerning John, What went ye out into the wilderness to see? A reed shaken with the wind? But what went ye out for to see? A man clothed in soft raiment? behold, they that wear soft clothing are in kings' houses. But what went ye out for to see? A prophet? yea, I say unto you, and more than a prophet. For this is he, of whom it is written, Behold, I send my messenger before thy face, which shall prepare thy way before thee. Verily I say unto you, Among them that are born of women there hath not risen a greater than John the Baptist: notwithstanding he that is least in the kingdom of heaven is greater than he. And from the days of John the Baptist until now the kingdom of heaven suffereth violence, and the violent take it by force. For all the prophets and the law prophesied until John. And if ye will receive it, this is Elias, which was for to come" (Matthew 11:1-14 KJV)
Despite the very high regard however, John's time, John's purpose, was fulfilled.
"For Herod had laid hold on John, and bound him, and put him in prison for Herodias' sake, his brother Philip's wife. For John said unto him, It is not lawful for thee to have her. And when he would have put him to death, he feared the multitude, because they counted him as a prophet."
"But when Herod's birthday was kept, the daughter of Herodias danced before them, and pleased Herod. Whereupon he promised with an oath to give her whatsoever she would ask. And she, being before instructed of her mother, said, Give me here John Baptist's head in a charger. And the king was sorry: nevertheless for the oath's sake, and them which sat with him at meat, he commanded it to be given her. And he sent, and beheaded John in the prison. And his head was brought in a charger, and given to the damsel: and she brought it to her mother. And his disciples came, and took up the body, and buried it, and went and told Jesus." (Matthew 14:3-12 KJV)
Fact Finder: How many rulers in the Herod dynasty are identified in Bible History?
See The Herods