New Revised Standard Version
In those days the Philistines gathered their forces for war, to fight against Israel. Achish said to David, “You know, of course, that you and your men are to go out with me in the army.”

New American Bible
In those days the Philistines mustered their military forces to fight against Israel. So Achish said to David, “You realize, of course, that you and your warriors must march out for battle with me.”

Douay-Rheims Bible
And it came to pass in those days, that the Philistines gathered together their armies, to be prepared for war against Israel: And Achis said to David: Know thou now assuredly, that thou shalt go out with me to the war, thou, and thy men.

And it came to pass in those days, that the Philistines gathered together their armies, to be prepared for war against Israel: And Achis said to David: Know thou now assuredly, that thou shalt go out with me to the war, thou, and thy men.

that the

1 Samuel 7:7 And the Philistines heard that the children of Israel were gathered together to Masphath, and the lords of the Philistines went up against Israel. And when the children of Israel heard this, they were afraid of the Philistines.

1 Samuel 13:5 The Philistines also were assembled to fight against Israel, thirty thousand chariots, and six thousand horsemen, and a multitude of people besides, like the sand on the seashore for number. And going up they camped in Machmas, at the east of Bethaven.

1 Samuel 17:1 Now the Philistines gathering together their troops to battle, assembled at Socho of Juda: and camped between Socho and Azeca, in the borders of Dommim.

1 Samuel 29:1 Now all the troops of the Philistines were gathered together to Aphec: and Israel also encamped by the fountain, which is in Jezrahel.

Philistines

Judges 3:1-4 These are the nations which the Lord left, that by them he might instruct Israel, and all that had not known the wars of the Chanaanites: . . .

thou shalt go

1 Samuel 27:12 And Achis believed David, saying: He hath done much harm to his people Israel: Therefore he shall be my servant for ever.

1 Samuel 29:2,3 And the lords of the Philistines marched with their hundreds and their thousands: but David and his men were in the rear with Achis. . . .