Pakistan launches assault on Taliban in Swat valley  President
Zardari braces for flood of half a million refugees as he meets
Obama in Washington  Pakistani helicopter gunships pounded a
Taliban-controlled emerald mine and other militant positions in
the Swat Valley today, killing dozens of militants, as fighting
intensified across North West Frontier province.  Amid
expectations of an imminent army operation, militants dug into
positions across the main town, Mingora, as terrified residents
fled the valley on foot across mountain paths. Taliban
reinforcements have been pouring into the area from adjoining
districts since Monday, many arriving under cover of night and
in some cases crossing into the battle zone by boat.  As
President Asif Ali Zardari met President Barack Obama in
Washington, his government was bracing for a flood of up to
500,000 internal refugees, making it the largest displacement
crisis in Pakistan's history.  The army said it killed more than
60 militants in Swat and neighbouring Buner,