God helps David smite the Philistines from the front and the rear

Now that Ishbosheth is dead, David is now king of both Israel and Judah, and he's fighting his old friends, the Philistines -- with God's help, of course.

God is David's military adviser. David asked him if he should attack the Philistines, and God said, "Attack: I will help you kill them."

David enquired of the LORD, saying, Shall I go up to the Philistines? wilt thou deliver them into mine hand? And the LORD said unto David, Go up: for I will doubtless deliver the Philistines into thine hand. 2 Samuel 5.19 

So David attacked and killed the Philistines. After the massacre, David said, "The Lord has burst forth before my enemies like a bursting flood" and he named it "Baalperazim" -- or some stupid name like that.

David smote them there, and said, The LORD hath broken forth upon mine enemies before me, as the breach of waters. Therefore he called the name of that place Baalperazim. 5.20 

When they finished slaughtering the Philistines at Baalperazim, David asked God if they should do it again. And God said, "Yeah, let's do it again. Only this time attack from behind when you hear troops marching in the tree tops."

When David enquired of the LORD, he said, Thou shalt not go up; but fetch a compass behind them, and come upon them over against the mulberry trees. Then shall the LORD go out before thee, to smite the host of the Philistines. And let it be, when thou hearest the sound of a going in the tops of the mulberry trees, that then thou shalt bestir thyself: for then shall the LORD go out before thee, to smite the host of the Philistines. 5.23-24 

God, I tell you, is a military genius!

So David waited until he heard noises in the mulberry trees and then followed God, smiting the Philistines from behind.

And David did so, as the LORD had commanded him; and smote the Philistines. 5.25 

The Bible doesn't say how many Philistines died in these two killings, so I'll just give it the usual 1000 for each.

God's next killing: Uzzah for trying to keep the ark from falling