Why did the U.S. Military drop white phosphorous on hundreds of civilians in the city of Falluja,Iraq?

It burns through clothes through the skin and then into the bone and can only be put out with wet mud,not water.... Now that is some cool testing we did right??? YEAH SURE,IT WAS USED TO ILLUMINATE THE AREA BELOW FOR OUR TROOPS AND THEN THE GLOBS DROPPED ON PEOPLE AND CHILDREN AS THEY RAN INSIDE LATER KILLED BY THE GAS... TOM