Battle of Megiddo in 1457 BC (or possibly 1482 or 1479) between Egypt and the Kingdoms of Canaan, led by the Kingdom of Kadesh, is the oldest recorded battle in human history. Sources are sparse and entirely one-sided (Egyptian) but essentially, Egypt controlled large amounts of land in the Levant at the time. When Thutmose III finally took full control of his throne following a regency (his father had died when he was 8, so his aunt, Hatshepsut, ruled alongside him until he came of age), a coalition of city-states in what is now Syria hoping to take advantage of the timing attempted to revolt against Egypt. Thutmose III launched a campaign into the Levant as a response. He was famously forced to decide between taking three routes into the Levant, of which he chose the one his advisors deemed the most dangerous. Fortunately for him, the King of Kadesh, leader of the rebellious coalition, had left that route relatively unguarded because he assumed his enemy would not traverse it. The decision took the Canaanites by surprise and Thutmose III's army marched to take the fortress city of Megiddo. With his forces split defending three routes, the King of Kadesh was forced to engage the Egyptian army with a smaller army and far worse position than he intended. The Egyptians proceeded to thoroughly trounce the Canaanites outside the walls of Megiddo (we are unclear as to the exact course of the battle or the tactics used), but failed to take the fortress of Megiddo amidst the enemy's retreat because they stopped to plunder their camp. After a seven month siege, the fortress fell and a number of Canaanite leaders who had taken shelter there were captured (though the King of Kadesh escaped), and Thutmose III had reasserted Egyptian dominance over the region.
The armies probably numbered about 10,000 men each, though the Egyptians may have outnumbered their opponents and its possible even 10k is an overstatement. Regarding casualties, the number is unclear. We know that the Egyptians (reportedly) took at least the following:
340 living prisoners and 83 hands, 2,041 horses, 191 foals, 6 stallions; 1 chariot worked with gold with a body of gold belonging to that enemy, 1 fine chariot worked with gold belonging to the prince of Megiddo, and 892 chariots of his wretched army – total: 924. 1 fine bronze coat of mail belonging to that enemy, 1 fine bronze coat of mail belonging to the prince of Megiddo, and 200 leather coats of mail belonging to his wretched army; 502 bows, and 7 poles of meru-wood worked with silver of the tent of that enemy.
According to AJ Spalinger, it's possible the Egyptians killed around 1,000 Canaanites, though he assumes that the army numbers were smaller than 10k, but the number could be as small as 83 (the number of hands claimed in the record). Thutmose III led a number of campaigns into the Levant to ensure pacification, but Megiddo was the most decisive battle of his reign.
Sources
http://www.militaryhistoryonline.com/ancient/articles/battleofmegiddo.aspx
Egyptain record: http://www.ancient.eu/article/1102/
http://www.reshafim.org.il/ad/egypt/megiddobattle.htm
http://faculty.uml.edu/ethan_spanier/Teaching/documents/SpalingerMegiddo.pdf