These Scripture tests may give further insight:
The Bible indicates that peace and justice sometimes require war (Mt 24:6).
This is made clear from many considerations. First, the Bible does not prohibit all taking of life. For instance, killing in self-defense is justified (Ex 22:2), as is killing in capital punishment (Gn 9:6). Government is divinely authorized to use “the sword” (Rm 12:4), as Jesus Himself recognized (Jn 19:11).
Second, under the law, God spelled out the rules of warfare for Israel (Dt 20).
Third, while Jesus forbade His disciples from using a sword for spiritual purposes(Mt 26:52), He urged His disciples to buy a sword if necessary for protection (Lk 22:36-38).
Fourth, John the Baptist did not say that armies should be abolished and did not call for repentance from serving in the office of soldier (Lk 3:14).
A ‘just war’ must be in defense of the innocent and/or against an evil aggressor (e.g., Gn 14).