Britain’s defense secretary Wednesday mourned the deaths of seven British soldiers killed over the last week in Afghanistan and defended the hard-fought mission against Taliban militants. But Bob Ainsworth, speaking at the Royal Institute of International Affairs in London, also said “the nature of the fight” against a “highly adaptable” enemy “means we will take more casualties before we succeed.” “It is understandable that at a time like this people ask why are the lives of these courageous people being lost Why are we in Afghanistan In these difficult times, can we afford to be there As defense secretary, I have a responsibility to answer these questions,” he said