NEW : Historian calls Obama 's speech good , but not a `` gold star '' in history . Comment: Nuclear weapons : Who has what ? ` Obama invokes JFK 's `` peace with justice '' call from 50 years ago . The president speaks at Berlin 's iconic Brandenburg Gate .
NEW : Historian calls Obama 's speech good , but not a `` gold star '' in history . Comment: Obama invokes JFK 's `` peace with justice '' call from 50 years ago . The president speaks at Berlin 's iconic Brandenburg Gate .