Megiddo (which is within the valley of Jezreel) is a city located in the territory given to the Israelite tribe of Manasseh when they entered the promised land. The word itself is translated from the Hebrew gadad (Strong's Concordance #H1413), meaning to slaughter or cut off. Before Joshua led the children of Israel into the land, it was a Canaanite royal city (Joshua 12:21). It took the Israelites quite a bit of time to finally overtake and possess the city.
Sometime after the city came under the control of Israel it was restored and greatly fortified under the reign of King Solomon, "And this is the reason for the labor force which King Solomon raised: to build the house of the Lord, his own house, the Millo, the wall of Jerusalem, Hazor, Megiddo, and Gezer" (1Kings 9:15)
Excavations have unearthed 26 layers of ruins, indicating a long period of settlement in the area. Anciently, it was important because it guarded the western branch of a narrow pass and trade route connecting Egypt and Assyria. The plain of Megiddo is part of the plain of Esdraelon (Jezreel valley), which is known as the great battlefield of Palestine. Many decisive battles, especially in ancient times, have been fought in or near this area.
The battle in the 15th century B.C. fought between the army of Egypt's Pharaoh Thutmose III and a coalition of Megiddo and Kadesh rulers. Thutmose III was the likely Pharaoh who was confronted by Moses and Aaron demanding the children of Israel be set free from slavery.
The battle in 609 B.C. between Egypt's army and Judah's King Josiah which is mentioned in the Bible (2Kings 23:29 - 30, 2Chronicles 35:20 - 35). The battle is also described in detail in the hieroglyphics found on the walls of Thutmose's temple in Upper Egypt. King Josiah is considered by some to have been the BEST king to rule over the Kingdom of Judah. He reigned for 31 years and was killed in the valley of Jezreel.
The battle in 1918 A.D., fought during World War I, between Allied troops led by General Edmund Allenby and the defending Ottoman Empire army.
The word Armageddon, which occurs only once in the Bible, is a combination of two Hebrew words. The first word is har, which means mountain or a range of hills, and mgiddown, which is called 'Megiddo' in English.
Armageddon is frequently used as a term to label the entire time period starting from when the armies of the world begin to gather together (along with the beast and false prophet) to FIGHT Jesus to his actual return and victorious war over the forces of evil. It is after this victory that Christ sets up His Millennial Kingdom on the earth.
In the sixteenth chapter of Revelation the word Armageddon is used to designate the actual location of the last world war, which is within the valley of Jezreel - Megiddo.
12. And the sixth angel poured out his vial into the great river Euphrates; and its waters were dried up, so that the way of the kings from the rising of the sun might be prepared. 13. Then I saw three unclean spirits like frogs come out of the mouth of the dragon, and out of the mouth of the beast, and out of the mouth of the false prophet; 14. For they are spirits of demons working miracles, going forth to the kings of the earth, even of the whole world, to gather them together to the battle of that great day of the Almighty God
16. And he gathered them together to the place that in Hebrew is called Armageddon (Revelation 16:12 - 14, 16, HBFV).