Moab and Edom

David's kingdom had it's first major war with Moab (east of the Dead Sea).

2 Sam 8:2

Then he defeated Moab. Forcing them down to the ground, he measured them off with a line. With two lines he measured off those to be put to death, and with one full line those to be kept alive. So the Moabites became David's servants, and brought tribute.

It is interesting that while David was a fugitive the people of Moab were friendly with him and offered him and his family refuge. David was a servant of the Lord and it was God's will that Moab become a vassal state with their own king, and paying tribute.

Afterward David defeated Edom (south east of the Dead Sea)

2 Sam 8:14

He also put garrisons in Edom; throughout all Edom he put garrisons, and all the Edomites became David's servants. And the LORD preserved David wherever he went.

There is not a lot of detail about this war but it occurred in the Valley of Salt (Arabah Valley) according to 2 Kings 14:7 and there was a severe slaughter. According to 1 Kings 11:15-18 Joab had to slay every male soldier in Edom, including the royal household. Only Hadad and a few servants escaped to Egypt. A garrison was left to maintain control and Edom was made a vassal state to Israel.

Defeating Moab and Edom gave David sovereignty on the east and south east sides of the Dead Sea, including the portion of the Kings Highway (see map) leading to the Gulf of Aqaba, an important water route for trade.