Sending his most categorical signal ever that he was committed to the peace process with Pakistan, Prime Minister Atal Behari Vajpayee today invited Islamabad to walk ‘‘together with India on the road to peace,’’ a road he said would be littered with landmines which will clear ‘‘once we start walking.’’ Although he reiterated that ending cross-border terrorism will be the test of Islamabad’s sincerity, Vajpayee’s break from the past—in his sixth Independence Day speech—couldn’t have been clearer. IN SIXTH INNINGS, HE OPENS THE BAT