For years, Anthony Zinni, a retired Marine General who once ran U.S. Central Command, blistered the administration of George W. Bush for its handling of Iraq. Now Zinni is teeing up on President Barack Obama's approach in Iraq, saying he is "worried" by Obama's cautious approach to the current crisis and the Sunni insurgent group Islamic State. "My God, we are the most powerful nation in the world," says Zinni, who was widely reported to have been passed over for the ambassadorship to Iraq in 2009 by Obama. "This is a moment we have to act. How many Americans getting...