As the United States and Iran enter what may be their last best chance at negotiations before a war against Tehran’s nuclear program, it is useful to remember that America has already fought one war with the Islamic Republic. 

In the late 1980s, President Ronald Reagan intervened in the Iran-Iraq war on the side of Saddam Hussein to tilt the conflict to an Iraqi victory. America engaged in a bloody if undeclared naval and air war against Iran, while Iraq fought a brutal land war. The lessons of our first war with Iran should be carefully considered before we embark on a second.

The Iran-Iraq War was devastating — one of the largest and longest conventional interstate wars since the Korean conflict ended in 1953. A half-million lives were lost, perhaps another million injured and the economic cost was over $1 trillion. Yet the battle lines at the end were almost exactly where they were at the beginning. It was also the only war in modern times in which chemical weapons were used on a massive scale.

The 1980-1988 conflict led to other disasters, including the Iraqi invasion of Kuwait in 1990 and the US invasion of Iraq in 2003. The bloody civil conflict in Iraq that followed may not have been the finale in this march of folly. The seeds of multigenerational tragedy were planted in the Iran-Iraq war and we will live with its consequences for decades, perhaps longer.