During 609 BC, the King of Egypt, King Necho (Necho II), was on his way to help the Assyrian King for the battle to retake Harran from King Nabopolassar's Babylonian forces. Harran was the new capital of Assyria after Assyria's Capital Nineveh was destroyed by Babylonian and Mede forces under King Nabopolassar.
But King Josiah of Judah who was at peace with King Necho till then decided to confront him en route at Megiddo. King Necho was intent on aiding Assyria's attempt to recapture Harran, as he was asked by God to do so. King Necho II asked King Josiah to refrain from engaging in war. Also, the Bible says that God had indeed spoken to King Necho to aid Assyria, but Josiah did not heed King Necho's advice. Instead, King Josiah attacked King Necho II and lost the battle at Megiddo. King Josiah died in 609 BC after being fatally injured in the battle of Megiddo (609 BC). King Necho II pressed ahead to aid Assyrians for the siege of Harran and reached there 3 months after it was captured by King Nabopolassar. The siege lasted 2 months and was not a success.
When King Josiah died, Jehoahaz, son of Josiah, ascended to the throne of Judah in the same year 609 BC. (Refer 2 Chronicles 35:20-25 and 2 Kings 23:29-30)
Three months after the battle of Megiddo and while on his way back from the failed attempt to recapture Harran from Babylonian control, King Necho II stopped at Judah and dethroned King Jehoahaz who had ruled just 3 months. King Necho then imprisoned King Jehoahaz and took him to Egypt as a captive.
All these events occurred in the year 609 BC itself, which is very significant since it is the starting year of calculation for Jeremiah's 70-year prophecy of Judah's captivity. The 70-year prophecy itself was issued 4 years later in 605 BC, announcing that the captivity which started in 609 BC with the dethroning of King Jehoahaz, would go on for a total time of 70 years. (Refer2 Chronicles 36:1-3, 2 Kings 23:30-33, Jeremiah 25:1)
While taking King Jehoahaz captive in 609 BC, King Necho of Egypt made Eliakim the brother of Jehoahaz King over Judah. He also changed the name of Eliakim to Jehoiakim and imposed heavy tributes on Judah. To pay these tributes, King Jehoiakim levied taxes on the people of Judah in proportion to their wealth. But he was an evil ruler and did things that are detestable to God.
In the third year of Jehoiakim's reign which is 606 BC, Prince Nebuchadnezzar II, son of King Nabopolassar attacked Jerusalem for the first time. King Nebuchadnezzar made King Jehoiakim a vassal king of the Babylonian empire and subjected him to payment of tributes (2 Kings 24:1 and Daniel 1:1-2). Nebuchadnezzar II was still a prince at the time and had not yet ascended the throne of Babylon. His father, King Nabopolassar, was King of Babylon at the time and was unwell due to prolonged illness. It was at this time that Daniel and his friends were taken to Babylon as exiles.
