Amalek

Amalek was a nation, presumably descending from Eliphaz' son Amalek, whom was conceived with his concubine Timna, that was at war with Israel when they first left Egypt.

First Battle with Israel
Amalek first battled Israel in the wilderness of Rephidim. Moses sent Joshua to fight Agag, which might be a title for Amalekite kings. The Lord told Moses that when his hand is raised, Israel would prevail against Amalek but if his hand is down, Amalek will prevail over Israel, so throughout the entire battle Moses has his hands up, with the help of two helpers. Eventually, Israel prevails over Amalek fully.