There is a reference to Bereshis Rabba 65:20 and Vayikra Rabba 33:5 to 2 Chronicles 13:17 which says that 500,000 soldiers of the northern tribes killed by the army of Yehuda. The Midrash states that the dead were mutilated so their wives would become agunas (unable to remarry) because their husbands would not be identified. This involves (lechoyra) an incredible disgrace of the dead AND punishment for the innocent wives, especially since their identities would not be done even if buried in a mass grave within the first 3 days. (This itself shows that the women of Yisroel were very pious for 500,000 of them to accept the status of agunah.)
Can anyone with access to the midrashim check the meforshim to explain what was going on over there?