Mattis believes Iran is the principal threat to the stability of the Middle East, ahead of Al-Qaeda and ISIL.
Mattis says: "I consider ISIS nothing more than an excuse for Iran to continue its mischief.
Iran is not an enemy of ISIS.
They have a lot to gain from the turmoil in the region that ISIS creates."
Mattis sees the Iran nuclear deal as a poor agreement, but believes there is now no way to tear it up, saying: "We are just going to have to recognize that we have an imperfect arms control agreement.
Second, that what we achieved is a nuclear pause, not a nuclear halt".
Mattis argues that inspections may fail to prevent Iran from seeking to develop nuclear weapons, but that "[i]f nothing else at least we will have better-targeting data if it comes to a fight in the future."
Additionally, he criticized Obama for being "naive" about Iranian intentions and Congress for being "pretty much absent" on the nuclear deal.

Mattis praises the friendship of regional US allies such as Jordan, Israel, and the United Arab Emirates.
He also criticized Obama for seeing allies as "free-loading", saying: "For a sitting US President to see our allies as freeloaders is nuts."
He has cited the importance of the United Arab Emirates and Jordan as countries that wanted to help, for example, in filling in the gaps in Afghanistan.
He criticized Obama's defense strategy as giving "the perception we're pulling back" from US allies.
He stresses the need for the US to bolster its ties with allied intelligence agencies, particularly those of Jordan, Egypt and Saudi Arabia.
In 2012 Mattis argued for providing weapons to Syrian rebels as a way to fight back against Iranian proxies in Syria.

The departure of several of Mattis's senior deputies in the fall of 2018 caused concern in foreign policy circles.
Many senior officials served only because of Mattis and fought political battles with the White House regularly.
One of the most serious areas of concern has been the potential for war with Iran because of the Trump Administration's withdrawal from the JCPOA at the same time the US military is redeploying forces from the Middle East to the Pacific to better compete with China and contain North Korea.
Mattis opposed the withdrawal from the JCPOA, calling the deal "the best we could come up with".

During an interview on C-SPAN, the Deputy Assistant Secretary of Defense for the Middle East Mick Mulroy said that Mattis focused on five distinct threats posed by Iran.
The first was obtaining a nuclear weapon.
The second was to maritime security in the Strait of Hormuz and the Bab al-Mandab, because a substantial portion of energy trade and commercial goods go through those areas.
The third was their support to proxies and terrorist organizations, including Hezbollah in Lebanon and Syria, Houthis in Yemen, some Hashd al-Shaabi in Iraq and safe-harboring senior al-Qaeda leaders in Iran.
The fourth was Iranian ballistic missiles in Houthi-controlled areas of Yemen for use against Saudi Arabia and in Syria with Hezbollah to use against Israel.
Cyber was the fifth threat and a growing concern.
Mattis believes Iran is the principal threat to the stability of the Middle East, ahead of Al-Qaeda and ISIL. Mattis says: "I consider ISIS nothing more than an excuse for Iran to continue its mischief. Iran is not an enemy of ISIS. They have a lot to gain from the turmoil in the region that ISIS creates." Mattis sees the Iran nuclear deal as a poor agreement, but believes there is now no way to tear it up, saying: "We are just going to have to recognize that we have an imperfect arms control agreement. Second, that what we achieved is a nuclear pause, not a nuclear halt". Mattis argues that inspections may fail to prevent Iran from seeking to develop nuclear weapons, but that "[i]f nothing else at least we will have better-targeting data if it comes to a fight in the future." Additionally, he criticized Obama for being "naive" about Iranian intentions and Congress for being "pretty much absent" on the nuclear deal.
Mattis praises the friendship of regional US allies such as Jordan, Israel, and the United Arab Emirates. He also criticized Obama for seeing allies as "free-loading", saying: "For a sitting US President to see our allies as freeloaders is nuts." He has cited the importance of the United Arab Emirates and Jordan as countries that wanted to help, for example, in filling in the gaps in Afghanistan. He criticized Obama's defense strategy as giving "the perception we're pulling back" from US allies. He stresses the need for the US to bolster its ties with allied intelligence agencies, particularly those of Jordan, Egypt and Saudi Arabia. In 2012 Mattis argued for providing weapons to Syrian rebels as a way to fight back against Iranian proxies in Syria.
The departure of several of Mattis's senior deputies in the fall of 2018 caused concern in foreign policy circles. Many senior officials served only because of Mattis and fought political battles with the White House regularly. One of the most serious areas of concern has been the potential for war with Iran because of the Trump Administration's withdrawal from the JCPOA at the same time the US military is redeploying forces from the Middle East to the Pacific to better compete with China and contain North Korea. Mattis opposed the withdrawal from the JCPOA, calling the deal "the best we could come up with".
During an interview on C-SPAN, the Deputy Assistant Secretary of Defense for the Middle East Mick Mulroy said that Mattis focused on five distinct threats posed by Iran. The first was obtaining a nuclear weapon. The second was to maritime security in the Strait of Hormuz and the Bab al-Mandab, because a substantial portion of energy trade and commercial goods go through those areas. The third was their support to proxies and terrorist organizations, including Hezbollah in Lebanon and Syria, Houthis in Yemen, some Hashd al-Shaabi in Iraq and safe-harboring senior al-Qaeda leaders in Iran. The fourth was Iranian ballistic missiles in Houthi-controlled areas of Yemen for use against Saudi Arabia and in Syria with Hezbollah to use against Israel. Cyber was the fifth threat and a growing concern.
Jim Mattis