BIBLICAL example of a violent-but-just military operation
Rescuing a Hostage: Explanation and Justification of the Policy Followed by the Children of Israel in their Rescue of Dinah.
“The sons of Yakov answered Shchem in deceit (‘mirmah')”
Circumstances of Circumcision: A Novel Defense of Yakov's Sons
Yakov's sons tricked the males of Shchem into circumcising themselves, and then Shimon and Levi killed them all while they were in pain from the operation.
Answer: Introduction
The crucial points are:
The children of Yakov, seeing that they would not be able to obtain Dinah's release, pretended to make a deal for their assimilation into the Shchem culture – their condition was circumcision. And it would not be enough that Shchem himself circucize, but that he must be from a people who are circumcised, so that all his people must follow suit . So, Shchem made an announcement in front of all his people, ‘welcoming' the Jews into their midst, but made it clear that he was offering all the Jewish women to his men. In return the Jewish men would have access to the local women.
Chamor was a crafty leader: in order that his people not be jealous of him, he was telling the men in his city that just as he took a Jewish woman, he would make available to them all the other Jewish women. All they had to do was circumcise themselves.
And they weren't circumcising themselves for him to be able to have Dinah, but in order for them to be able to have access to the new women in their midst. In a culture led by a kidnapping rapist the men wouldn't eagerly undertake a painful operation just to welcome some strangers into their midst or to allow the leader to mary someone, but only if they themselves had intention to take a Jewish women. And even if there was social pressure to circumcise themselves, if they did not intend to marry a Jewish woman no one would ever know whether or not they were circumcised, so why bother doing it. Most likely it was not the agreement per se but the promise of the resulting availability of these newly-arrived women which motivated them, and moreso, it motivated only those intending to take Jewish women for themselves. And it was precisely these men that Dina's brothers needed to identify and neutralize.
Shchem knew that he needed his people's help to defend him in case Dinah's family would try to rescue her. By promising the Jewish women to the men, he bought their allegiance and their support in case of attack: now it was not anymore simply a matter of the men rallying to defend their leader from the ramifications of his escapade, but rather now there was to be a prize for all of them.
The brothers, planning their rescue, wanted to immobilize the men who were most likely to resist, and it was clearly those men who were planning to avail themselves of the Jewish women who would be most likely to resist the rescue, or to pursue the Jews when they fled to safety with Dinah in their hands, and so they came up with this stratagem, knowing that only those men who intended to take Jewish women were likely to go to the length of circumcising themselves.
There might have been differences in strategy by the brothers who were full brothers (having not only the same father but also the same mother as Dinah) and those who were only half brothers. The intent of the half brothers may have been merely to incapacitate them so that they wouldn't interfere with the rescue, however Shimon and Levi went further.
As has been pointed out by commentators, the passage “the city which polluted their sister” [34:27] can have the implication that the city as a whole was guilty of the pollution of Dinah, in other words that there was more than one man involved in the rape. And, in fact the relevant passage also implies that all the men of Shchem circumcised themselves.
Dinah's full-brothers decided that the males who had circumcised themselves were likely the culprits and deserved death, and in any case they were the ones who were indicating by their actions that they would want the Jewish women, and so were more dangerous.
And so they decided to take no chances and kill all those who had circumcised themselves.
Why take the wives and children?
Firstly economic reasons, in those days a widow with children, or perhaps any widow was in dange rof starvation. And this seems to have bene the way of warfare in those days. Also, this was a reaction to the plan of the people of the city: “we'll take their women, they'll take our women”, so this was an ironic twist, they were killed and lost their women. Furthermore: By circumcising themselves the men were indicating desire to acquire Jewish wives in addition to their existing local wives; this terminated their full emotional right to their wives.
Further Indication that they were justified
[34:30] Yakov chides the two brothers, worrying that the nations will retaliate. But he does not claim that their deed was unjustified. And when the brothers reply “will Dinah be treated as a whore” [34:31] Yakov has no reply. Presumably, they are saying that there was no other way to actually rescue their sister. And indeed God provides protection for them from the nations [35:5], which seems to imply divine acceptance of their deed.