Mattis is very, very, very anti-Iran.
He told the US Congress that Iran should be “brought to its knees”.
Here are just a few of the strong anti-Iran sentiments that Mattis has expressed:
Speaking to Congress today, Central Command leader Gen. James Mattis insisted sanctions are not successful against Iran, and suggested that diplomacy had been all but useless, insisting that Iran’s “history of deceit” meant they could never be trusted at any rate.
Mattis conceded that he is “paid to take a rather dim view of the Iranians,” which is putting it mildly, and sought to stop short of criticizing the administration’s current tack, saying he “basically” supports the current direction vis-a-vis Iran.
Rather he said the goal was for Iran to be “brought to its knees” and that “open” warfare was just one of a few different options that he is considering to that end, though he insisted there was a plan ready to go on attacking Iran. He did not specify what the other options were, but the US had been engaged in covert warfare against Iran for years.
[source : Centcom Chief Rejects Diplomacy, Says Iran Must Be ‘Brought to Its Knees’, AntiWar, http://news.antiwar.com/2013/03/05/centcom-chief-rejects-diplomacy-says-iran-must-be-brought-to-its-knees/, 5th March 2013]