After leaving Marah where God revealed Himself as the Healer of His people (Jehovah-Rophe), the people had a period of rest but they soon forgot what God had performed for them when they came into hunger and thirst.  God came to their rescue.  As their Provider, He had given them manna and quail from heaven (Ex. 15:6-15 and Ex. 16:8, 11-15).  When they needed drink, he brought them to a rock where they experienced another miracle of provision – water in abundance (Ex. 17:9).  Shortly after that, they were faced with the Amalekites!  After all they had been through with their Delivering God, they seemed to have learned and they responded in a calm and organized way under the leadership of their much admired Joshua.  This is the first war that Israel is to experience, and they are ill trained for such a venture against a highly experienced army. The two leaders have a plan.  Joshua takes his army and marches against the Amalekites, and Moses takes his place as an intercessor for the army.  As long as Moses holds up his arms, Israel prevails; when his arms drop, Amalek prevails.  Aaron and Hur came to Moses’ aid as they seat Moses on a stone and assist in holding up his hands.  God comes to the aid of Israel again and shows Himself as Jehovah-Nissi, my Banner.  He is the victorious conqueror!

Introduction to page in sweet aroma @https://onetahayes.com/gods-provision/god-my-victor-jehovah-nissi/