Exodus 17:14-15 NKJV

“Then the Lord said to Moses, “Write this for a memorial in the book and recount it in the hearing of Joshua, that I will utterly blot out the remembrance of Amalek from under heaven.” 

And Moses built an altar and called its name, (Jehovah Nissi) The-Lord-Is-My-Banner;” Moses, recognizing that the Lord was Israel’s banner under which they defeated the Amalekites, he built an altar and named it Jehovah-Nissi (the Lord our Banner).

Nissi is sometimes translated as a pole with an insignia attached. In battle opposing nations would fly their own flag on a pole at each of their respective front lines. This was to give their soldiers a feeling of hope and a focal point. This is what God is to us: a banner of encouragement to give us hope and a focal point.