Erik Fosse, a Norwegian cardiologist, worked in Gaza hospitals during the recent war."It was as if they had stepped on a mine," he says of certain Palestinian patients he treated. "But there was no shrapnel in the wound. Some had lost their legs. It looked as though they had been sliced off. I have been to war zones for 30 years, but I have never seen such injuries before."

Dr. Fosse was describing the effects of a U.S. "focused lethality" weapon that minimizes explosive damage to structures while inflicting catastrophic wounds on its victims. But where did the Israelis get this weapon? And was their widespread use in the attack on Gaza a field test for a new generation of explosives?