They weren't being cruel, they were obeying their war-god. The one they kept in the Ark of the Covenant, YHWH. Actually the hebrew god, and his angels were always warrior like, not the kind hearted bearded man that is portrayed by Jesus and now the catholic church.
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http://www.oneworldmagazine.org/focus/etiopia/arkref.html
a brief history of Yawheh with the early hebrews :
Judaism
more on god's unloving nature :
http://www.geocities.com/paulntobin/godbible.html
that should be enough for now..
I am always fascinated by how christians resolve the changing nature of god from the OT to the NT.
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