American and British warplanes hit targets in southern Iraq, in response to Iraqi guns firing on US aircraft over the southern no-fly zone. Iraq appears to be firing on US warplanes so as to encourage attacks on anti-aircraft weapons placed in populated areas. This can produce civilian casualties that, in turn, provide Iraq with propaganda fodder to help get the embargo lifted. To counter this, US warplanes often use concrete filled bombs (which must make a direct hit to be effective.)