Prelude to the War Against Benjamin
The disastrous war against the Benjamites began with a single incident, the brutal gang rape of a Levite's concubine. As horrible as this incident was, we still might wonder how it was able to spark such a major war.
There are two major relevant factors involved in what happened, one cultural and the other historical. The cultural factor involves proper treatment of a guest. Life in the Middle East has always been difficult, and to cope with the arduous conditions of nomadic life an elaborate system of social customs was developed. One social custom required every person to kindly entertain a guest, to provide comfort, lodging and food for a brief period to any stranger who happened upon one's camp, even if that stranger was a member of an enemy tribe in a time of peace. If the due benevolence was not shown, it was deemed an act of hostility and impiety before God. If the offense was serious enough, clan or tribal wars could be ignited.
A second factor was the persistent memory of what God had done to Sodom and Gomorrah—not only from the Pentateuch but even, no doubt, from regional stories passed down through generations. The filthy, abominable behavior of the inhabitants of these cities and others around them was a major factor in the cry that went up to God against them. The destruction against Sodom and her neighbors was so complete that even today their exact whereabouts remain unknown. By comparing the behavior of the Gibeahite "sons of Belial" (Judges 19:22 Judges 19:22Now as they were making their hearts merry, behold, the men of the city, certain sons of Belial, beset the house round about, and beat at the door, and spoke to the master of the house, the old man, saying, Bring forth the man that came into your house, that we may know him.
American King James Version×) and the old man (Judges 19:23 Judges 19:23And the man, the master of the house, went out to them, and said to them, No, my brothers, no, I pray you, do not so wickedly; seeing that this man is come into my house, do not this folly.
American King James Version×) with the conduct of the men of Sodom (Genesis 19:4-5 Genesis 19:4-5  But before they lay down, the men of the city, even the men of Sodom, compassed the house round, both old and young, all the people from every quarter:  And they called to Lot, and said to him, Where are the men which came in to you this night? bring them out to us, that we may know them.
American King James Version×) and Lot (verses 6-8), one should be able to see a very clear parallel.
Factoring the understanding of these elements into the story, one can see why an incident of this nature could ignite such a war. The Levite was a representative of God, to whom the Gibeahites were extremely inhospitable and showed open and flagrant impiety. Knowing the social requirements to care for the traveler, the natural conclusion was that such an affront would be repaid with vengeance by the One the Levite served—God. Therefore action needed to be taken.
Of course, the Levite does not appear very God-oriented, surrendering his concubine to be abused as he did and being so cold and uncaring toward her the next morning before he knew she was actually dead. The Ephraimite's offer to surrender up his own daughter does not paint him any better. We see here the low status that women had in that society. Truly, this story is utterly horrendous all the way around. It illustrates how low things had sunk—to the depravity of Sodom and Gomorrah. The prophet Hosea later cited this episode as one of the most corrupt events in Israel's history (Hosea 9:9 Hosea 9:9They have deeply corrupted themselves, as in the days of Gibeah: therefore he will remember their iniquity, he will visit their sins.
American King James Version×; Hosea 10:9 Hosea 10:9O Israel, you have sinned from the days of Gibeah: there they stood: the battle in Gibeah against the children of iniquity did not overtake them.
American King James Version×).