Moses' arms and staff must be held up to win the battle!
In Exodus 17 it is a little hard to know why God used the imagery that He chose to use. The Israelites are traveling in the wilderness after leaving Egypt, and the Amalekites attack them:
8 Then came Amalek, and fought with Israel in Rephidim.
9 And Moses said unto Joshua, Choose us out men, and go out, fight with Amalek: to morrow I will stand on the top of the hill with the rod of God in mine hand.
10 So Joshua did as Moses had said to him, and fought with Amalek: and Moses, Aaron, and Hur went up to the top of the hill.
11 And it came to pass, when Moses held up his hand, that Israel prevailed: and when he let down his hand, Amalek prevailed.
12 But Moses' hands were heavy; and they took a stone, and put it under him, and he sat thereon; and Aaron and Hur stayed up his hands, the one on the one side, and the other on the other side; and his hands were steady until the going down of the sun.
13 And Joshua discomfited Amalek and his people with the edge of the sword.
14 And the LORD said unto Moses, Write this for a memorial in a book, and rehearse it in the ears of Joshua: for I will utterly put out the remembrance of Amalek from under heaven.
15 And Moses built an altar, and called the name of it Jehovahnissi:
16 For he said, Because the LORD hath sworn that the LORD will have war with Amalek from generation to generation.
End Quote
So, I'm wondering if this was real history, yes of course, but also prophetic imagery for the church age, for the centuries after Christ's coming. After all, when Moses held up both hands with each hand holding the staff it would have put him in the same upper body configuration as a crucified man. And there was a man on each side to keep Moses and his staff held up for the world to see. So the two men might have been real men all right, yes of course, but they may also have signified the Eastern and Western Christian church. Rome and her allied churches, and Constantinople and her allied churches. And whenever the churches do a good job of holding up the sacrifice made by Jesus of Nazareth for the sins of all who choose to follow Him, the Christian church grows. But whenever the churches get lazy and quit holding that up for all the world to see, quit evangelistically witnessing to the nations about the sacrifice Jesus made, then the tide goes against Christianity, and God's defiant enemies gain ground.
It's only a thought, but some parts of it might work. I'm still thinking about it. It also may not be prophetic at all, just an unusual action that changes the tide of battle. God knows!!