Does the Bible actually provide the reasons behind the War of Armageddon?

From what I have read it describes the time and how to recognize it but not the reasons.

Don't just try the New Testament. The Old Testament is going to tell you details that aren't in the New Testament. 

Zechariah 14

2 I will gather all the nations to Jerusalem to fight against it; the city will be captured, the houses ransacked, and the women raped. Half of the city will go into exile, but the rest of the people will not be taken from the city. 3 Then the Lord will go out and fight against those nations, as he fights on a day of battle. 4 On that day his feet will stand on the Mount of Olives, east of Jerusalem, and the Mount of Olives will be split in two from east to west, forming a great valley, with half of the mountain moving north and half moving south.

Daniel 11

41 He [the Antichrist] will also invade the Beautiful Land. Many countries will fall, but Edom, Moab and the leaders of Ammon will be delivered from his hand. 42 He will extend his power over many countries; Egypt will not escape. 43 He will gain control of the treasures of gold and silver and all the riches of Egypt, with the Libyans and Cushites[e] in submission. 44 But reports from the east and the north will alarm him, and he will set out in a great rage to destroy and annihilate many. 45 He will pitch his royal tents between the seas at[f] the beautiful holy mountain. Yet he will come to his end, and no one will help him.

So, regardless of why those armies are there in Megiddo for Armageddon, they encounter Antichrist, maybe because he is the residing power there, maybe because the kings of the east are trying to conquer the world. 

Revelation 16

12 The sixth angel poured out his bowl on the great river Euphrates, and its water was dried up to prepare the way for the kings from the East. 

They were prepared to go that way anyway, then the Euphrates dries up. 

The bible proves nothing.