Saddam Hussein's invasion of Iran on September 22, 1980, was not inevitable—it was a calculated gamble by a ruthless pragmatist who read the regional chessboard and believed the moment had arrived to reshape the balance of power in the Persian Gulf.

The Collapse of the Shah and Saddam's Fear

The Iranian Revolution of 1979 had shattered what regional analysts considered the pillar of American stability in the Middle East. Shah Mohammad Reza Pahlavi, who had ruled Iran with an iron fist backed by US support, was overthrown by Ayatollah Khomeini and a coalition of revolutionary forces. For Saddam, who had been consolidating power in Iraq since 1968 and had taken full control as president in July 1979, the revolution posed an existential threat.

The Shah's fall removed a powerful rival and created a power vacuum. But worse, from Saddam's perspective, Khomeini's theology of Islamic revolution explicitly threatened secular Arab regimes like Iraq. The new Iranian government was actively exporting revolution to Iraq's Shia population, which comprised roughly 60 percent of Iraq's citizens. Shia clerics in Najaf and Karbala—Islam's holiest cities, located in Iraq—were receiving support from Tehran to organize against Saddam's Baathist regime.

The Shia Threat

Iraq's Shia majority had historically been marginalized by the Sunni-dominated Baath Party. Saddam's government, controlled by a Sunni minority, viewed any strengthening of Shia political consciousness as a direct challenge to state stability. Iranian revolutionaries were not subtle about their intentions: Radio Tehran broadcast propaganda aimed at Iraqi Shias, calling them to rise up against their oppressors.

In spring 1980, the Dawa Party—an Iraqi Shia opposition group with links to Iran—began a series of bombings and assassination attempts against Iraqi government officials. One attempt targeted Deputy Prime Minister Tariq Aziz in April. The regime's response was brutal: thousands of Shias were arrested, and on June 1, Ayatollah Muhammad Baqir al-Hakim, a leading Shia cleric with ties to Iran, was executed.

The Territorial Calculation

Beyond the ideological threat, Saddam saw territorial opportunity. The Shatt al-Arab waterway, which forms the border between Iraq and Iran and provides Iraq's only outlet to the Persian Gulf, had been a point of contention for decades. A 1975 agreement between Iraq and the Shah's Iran had forced Iraq to cede half of the waterway to Iran. Saddam had signed that agreement under duress; now that the Shah was gone and Iran was in chaos, the opportunity to restore Iraqi sovereignty over the entire waterway was tantalizing.

Additionally, Iraq coveted the oil-rich Khuzestan Province in southwestern Iran, which had a significant Arab population. Saddam believed he could seize the territory and inspire an Arab uprising that would overthrow Khomeini's regime before international powers could effectively intervene.

The Muted World

Critically, Saddam believed the international community would not punish an invasion. The United States was still reeling from the hostage crisis in Iran and was openly hostile to Khomeini's government. The Soviet Union, though it had a treaty with Iraq, was distracted by its invasion of Afghanistan and unlikely to seriously oppose Iraqi expansion into Iran. France, Germany, and the Gulf states all had their own reasons to see a weakened Iran.

This calculation proved correct. When Iraqi forces crossed the border in a massive assault that included air strikes on Iranian airfields, the UN Security Council was paralyzed. The invasion was condemned in principle but no sanctions were imposed, no intervention force assembled.

The Gamble

Saddam believed the war would last weeks, perhaps a few months. He underestimated the revolutionary fervor that Khomeini had instilled in the Iranian population and the willingness of Iranians to die for their revolution. He also underestimated his own military's limitations when faced with an enemy that matched Iraq in size and exceeded it in population and resources.

The invasion of Iran would consume Iraq for eight years, cost the country billions of dollars, kill hundreds of thousands of its soldiers, and ultimately leave Saddam's territorial ambitions unfulfilled. Yet in September 1980, none of this was visible to him. He saw only a rival in disarray and a moment that would never come again. He was wrong about the duration and cost of his gamble, but right about the international community's indifference. That indifference, more than any other factor, allowed the war to begin.