war ethics -- melachim beis perek vav

This is anything but a comprehensive discussion of this topic.  I just want to throw out an interesting machlokes I came across.

In melachim beis (perek 6), melech aram sends an army to kill elisha.  Elisha uses his miraculous powers and basically has them march right into shomron into the hands of melech yisrael:

 כא) וַיֹּאמֶר מֶלֶךְ־יִשְׂרָאֵל אֶל־אֱלִישָׁע כִּרְאֹתוֹ אוֹתָם הַאַכֶּה אַכֶּה אָבִי:    (כב) וַיֹּאמֶר לֹא תַכֶּם הַאֲשֶׁר שָׁבִיתָ בְּחַרְבְּךָ וּבְקַשְׁתְּךָ אַתָּה מַכֶּה שִׂים לֶחֶם וָמַיִם לִפְנֵיהֶם וְיֹאכְלוּ וְיִשְׁתּוּ וְיֵלְכוּ אֶל־אֲדֹנֵיהֶם:

Melech Yisrael asks elisha, "should I kill them all".  Elisha responds that he should not.  why not?

Rashi:  (כב) האשר שבית וגו' - וכי דרכך להרוג אותם שאתה מביא שבייה (ומשבית אותם  -- Do you kill prisoners of war?  Of course not!!

Radak: כב) האשר שבית - מה דין יש לך בהם שתכה אותם וכי אתה שבית אותם בחרבך ובקשתך:  You have no claim on these people such that you should kill them.  If you had beaten them in war and taken them as POWs, then of course you should kill them.  Since that was not the case, however, you should let them go.

Two opposite reads of the same pasuk, with major implications for the ethics of war!  Anyone who knows me knows where I stand on this issue...