The Army first claimed the rounds were used only for illumination, but after an article (PDF) describing their use appeared in Field Artillery magazine recanted, saying the rounds were used as psychological weapons to scare out insurgents who were then killed by the usual means.
According to one embedded journalist:
[Troops were ordered] to fire round after round of high explosives and white phosphorus charges into the city Friday and Saturday, never knowing what the targets were or what damage the resulting explosions caused. ...Sound psychological? Sounds a lot more like indiscriminately firing rounds of ultra-hot phosphorus onto unseen targets. A reporter for the UK's Independent says:
They say they have never seen what they've hit, nor did they talk about it....
Phosphorus burns bodies, in fact it melts the flesh all the way down to the bone ... I saw the burned bodies of women and children. Phosphorus explodes and forms a cloud. Anyone within a radius of 150 metres is done for.The Army may not have broken any laws, but that's a hell of a way to win hearts and minds.
[via Daily Kos]