Charles Krauthammer said the Iranians are trying to essentially reclaim territory now run by ISIS terrorists in Syria.
He was reacting to the downing of a Syrian jet by American forces, which drew the ire of the Russians.
"This is like the last year of World War II. We're all fighting the Nazis but we know they're finished," he said.
He said the Persians (Iranians) owned the lands from Syria to Iran 2,000 years ago and now want them back.
He said the Saudis and the Americans do not want Iran to effectively have a large slice of the Middle East, so they protected U.S.-backed forces in Syria by shooting down the jet.
Krauthammer said that if the Iranians stake a claim to ISIS lands after the terrorists are eventually driven from Raqqa, Syria will become a "puppet regime" of Russia and Iran.
"Our interest is to make sure that doesn't happen," he said.
Watch the full segment above.