Iranian President Mahmoud Ahmadinejad arrives in Cairo today for the first meeting between an Egyptian and an Iranian head of state in more than 30 years. Their countries are two of the Middle East's largest and most powerful, but they split in 1979 when Egypt sheltered the shah of Iran, driven into exile by the Islamist revolution, and made peace with Israel.

That division, which has done so much to shape Middle Eastern politics, of course goes deeper than any one incident or conversation. But many of its roots are visible in this historic video from 1979, of CBS News' Mike Wallace interviewing Ayatollah Ruhollah Khomeini, the driving force of  Iran's revolution and soon to be the country's supreme leader. Wallace asked him about Egyptian President Anwar Sadat, who had called Khomeini a "lunatic" and "a disgrace to Islam."

Khomeini countered that Sadat "compromises with the enemies of Islam," likely a reference to the 1978 U.S.-brokered Egypt-Israel peace accords. He called on Egyptians to overthrow Sadat in a popular revolution like Iran's. When Sadat was assassinated in 1981, Iran named a street after his killer.

There are other causes for the division as well. Egypt opposed Syrian leader Bashar al-Assad, a close Iranian ally. And Egypt is a majority Sunni country, while Iran is Shiite -- a division that could be exacerbated with the rise in Egypt of Islamists. A Salafi political party released a statement calling on Egyptian President Mohamed Morsi to challenge Ahmadinejad on his support of Syria, explaining, "Egypt is committed to the protection of all Sunni nations."