New Revised Standard Version
(it was only that successive generations of Israelites might know war, to teach those who had no experience of it before):

New American Bible
to teach warfare to those generations of Israelites who had never experienced it:

Douay-Rheims Bible
That afterwards their children might learn to fight with their enemies, and to be trained up to war:

That afterwards their children might learn to fight with their enemies, and to be trained up to war:

might know

Genesis 2:17 But of the tree of knowledge of good and evil, thou shalt not eat. For in what day soever thou shalt eat of it, thou shalt die the death.

Genesis 3:5,7 For God doth know that in what day soever you shall eat thereof, your eyes shall be opened: and you shall be as Gods, knowing good and evil. . . .

2 Chronicles 12:8 But yet they shall serve him, that they may know the difference between my service, and the service of a kingdom of the earth.

Matthew 10:34-39 Do not think that I came to send peace upon earth: I came not to send peace, but the sword. . . .

John 16:33 These things I have spoken to you, that in me you may have peace. In the world you shall have distress. But have confidence. I have overcome the world.

1 Corinthians 9:26,27 I therefore so run, not as at an uncertainty: I so fight, not as one beating the air. . . .

Ephesians 6:11-18 Put you on the armour of God, that you may be able to stand against the deceits of the devil. . . .

1 Timothy 6:12 Fight the good fight of faith. Lay hold on eternal life, whereunto thou art called and be it confessed a good confession before many witnesses.

2 Timothy 2:3 Labour as a good soldier of Christ Jesus.

2 Timothy 4:7 I have fought a good fight: I have finished my course: I have kept the faith.

to teach.