As of this writing, America is planning military action against Syria under the pretext that the Syrian government allegedly used chemical weapons in an attack in a Damascus suburb on August 21. Leading figures in the Obama administration can be heard referring to chemical weapons as a “moral obscenity,” such that the United States has a “moral obligation” to punish the country that uses them.

Recently declassified CIA files prove that, during the Iran-Iraq war (1980-1988), US intelligence agencies actively assisted in some of the most horrific chemical weapons attacks in history, which resulted in the deaths of tens of thousands of people. These CIA files are the subject of an important new exposé by reporters Shane Harris and Matthew M. Aid in Foreign Policy dated August 26, 2013.

In a key military engagement in 1988, during the final period of the war, the CIA determined that Iranian forces were massing and about to break through Iraqi lines. Specifically, US intelligence agencies determined from satellite images that a planned Iranian offensive was likely to result in the capture of the strategic city of Basra, which in turn could have led to the collapse of the Iraqi military.

This information was transmitted to US President Ronald Reagan, who personally wrote in the margin of one intelligence briefing, “An Iranian victory is unacceptable.” Accordingly, the US intelligence agencies were authorized to transmit as much detailed information as possible regarding the Iranian military positions to the Iraqi regime of Saddam Hussein. This information was transmitted with full knowledge that Iraq’s military would take advantage of this intelligence to launch a series of illegal chemical weapons attacks.

Rick Francona, an American military attaché who was in Baghdad during this period, was interviewed for Harris and Aid’s report. “The Iraqis never told us that they intended to use nerve gas. They didn’t have to. We already knew,” Francona said.

In a single day of the Iran-Iraq war, 1,500 missiles containing deadly chemical agents rained down on Iranian positions. Iraq assembled its arsenal of chemical weapons—including nerve gas, mustard gas, and anthrax —out of supplies purchased directly from western firms, including US corporations. (These “weapons of mass destruction” would later become the pretext for the US invasion and occupation of the country in 2003.)

According to Harris and Aid’s report, the declassified files “show that senior U.S. officials were being regularly informed about the scale of the nerve gas attacks. They are tantamount to an official American admission of complicity in some of the most gruesome chemical weapons attacks ever launched.”

Much of the information provided to the Hussein regime by the Americans constituted “targeting packages,” according to Francona. In other words, the United States was not just handing out satellite photographs, but was making specific recommendations about when, where, and how Iraq should carry out chemical weapons attacks.

A chemical weapons attack by Iraq on the Kurdish village of Halabja on March 16, 1988 resulted in the deaths of 5,000 civilians, producing some of the most famous and heart-wrenching images of the war. Intelligence from America was “freely flowing” to Iraq, according to Francona. At the time, the US State Department falsely claimed that Iran had carried out the attack. This remained the official US position until the late 1990s.

The declassified intelligence briefings analyze whether any harm would result to US credibility if US complicity in the Iraqi chemical weapons attacks came to light. The briefings then note that the USSR had used illegal chemical weapons in Afghanistan with only minor repercussions, and so recommended that the US could safely do the same.

During the war, Iranian diplomats appealed to the UN to investigate Iraq’s use of illegal chemical weapons. However, the UN did not take any action, citing “lack of evidence”— evidence that was in America’s possession all along.

The Iran-Iraq war, which broke out in 1980 after the Carter administration encouraged Iraq to invade Iran, was one of the most tragic and brutal in the second half of the 20th century, with both countries adopting “total war” strategies that included the targeting of civilians. The average military offensive resulted in 15,000 casualties on each side. An estimated one million people died in the conflict, and two million were maimed or wounded. While secretly working to secure the victory of Iraq, the US adopted an official position of neutrality and sold weapons to both sides.

In the later period of the war, US policy shifted towards more open backing for Iraq, including direct shipments of arms and financial assistance to the Hussein regime. In return, Hussein entered into a major oil pipeline deal with the Americans. In the final period of the war, during which the use of chemical weapons by Iraq was most intense, Reagan ordered the US Navy to intervene directly to protect tankers containing Iraq’s oil exports, effectively signaling that the US would not permit Iran to win. In 1988, Iran accepted a UN Security Council resolution ending the conflict after the USS Vincennes shot down an Iranian passenger plane, killing 290 people.

In the words of Harris and Aid, the declassified CIA documents make clear that “it was the express policy of Reagan to ensure an Iraqi victory in the war, whatever the cost.”