Army helicopters flew sorties over cut-off areas in Pakistan’s mountainous north Wednesday and rescue parties fanned out across waterlogged plains in the south as misery mounted for millions trapped by the worst floods in the country’s history. Monsoon rains have submerged a third of Pakistan, claiming at least 1,160 lives since June and unleashing powerful floods that have washed away swathes of vital crops and damaged or destroyed more than a million homes.