During its war with Hamas, the Israeli military pursued a strategy of deliberately blasting crowded buildings — including a school and a hospital — with incendiary white phosphorus rounds. It was part of a concerted effort to scorch hideouts in and around Gaza City, Human Rights Watch senior military analyst Marc Garlasco tells Danger Room.

"The attitude was: When in doubt, burn it down," says Garlasco, who spent weeks in Gaza after the fighting to conduct forensic research.

Of all the controversial things the Israeli military did during the conflict, firing off white phosphorus

(WP) may have been the most divisive. When exposed to oxygen, phosphorous catches fire, throwing up thick clouds of smoke — which makes it both good for illumination and for concealing troop or tank movements. But WP can also burn people, quickly and horribly, sticking to the skin as it singes. So firing phosphorus weapons carelessly in a civilian area is problematic, at best — and possibly illegal.

Garlasco says the Israeli Defense Forces were more than careless with WP, however. Troops repeatedly targeted Hamas hideouts in crowded urban areas where civilians would almost certainly get caught in the cross-fire. It was part of a larger Israeli effort to use maximum force to protect its troops during the Gaza campaign.

Amnesty International called the Israeli use of WP in Gaza a "war crime"; the Israeli human rights group B'tselem was only marginally more careful, saying it was "impossible to use in a legal sense." In response, the Israeli Defense Forces at first denied it used WP. Then it defended its phosphorus use as proper — while launching an internal investigation into potential abuses.

On Thursday, Human Rights Watch is set to just released the most comprehensive report to date on how the Israeli military (and, to a lesser extent, Hamas) employed phosphrous rounds. [UPDATE: Read it here; we'll pull details, shortly.]

Garlasco says the Israeli Defense Forces (IDF) used the munitions in three ways, broadly. First, the troops fired rounds in rural areas, possibly to set off mines or improvised bombs. Second, the IDF used phosphorus one the edges of cities — to screen its movements, perhaps.

But a third — and definitely most troubling — set of cases involved the Israeli military shooting air-burst WP rounds into crowded urban areas. Time and time again, when the IDF found what it felt was a Hamas outpost in a big building, troops blasted phosphorus overhead. A school, a hospital and a UN building in Gaza City were all hit. To Garlasco, it was part of a deliberate initiative to burn down any sites of resistance.

The problem is, many civilians were in the way.

Dr. Nafez Abu Shaban, head of the burn unit at Gaza City's Sifa

Hospital, says he treated dozens of white phosphorous cases. Other doctors made similar reports.

What makes it all the more troubling to Garlasco, a former chief of High Value Targeting on the Joint Chiefs of Staff, is that he couldn't find a clear reason *why *the

Israeli military was using WP in this way. The WP shots didn't accompany large-scale maneuvers, so the purpose couldn't have been to screen those troops (besides, air-bursting the rounds only increase the incendiary effects, while minimizing the smoke.) The buildings hit with WP were big — too big to "send in a shell, to take out booby traps," Garlasco says. "It still boggles my mind, what the military utility was."

[Photo: Mohammed Abed/AFP/Getty Images]

ALSO: