Ali Hassan al-Majid, an Iraqi defense minister under the former Baathist regime, was executed in January 2010 for ordering chemical weapons attacks on the Kurdish population in 1988. An estimated 5,000 people were killed during the assault, earning Majid the nickname Chemical Ali.
The U.S. government issued a statement marking the 25th anniversary of the attacks on Halabja, saying it would help ensure any of the remaining perpetrators are held accountable.
"This terrible crime was but one of many in Saddam Hussein's Anfal Campaign, in which tens of thousands of innocent Iraqis were slaughtered," the statement read.
Wednesday marks the 10th anniversary of the U.S.-led invasion of Iraq. The intervention was meant as a response to Iraq's alleged program of weapons of mass destruction. No such weapons were uncovered.
A series of reports published ahead of the anniversary have been critical of the conflict. A BBC documentary scheduled for a Monday broadcast alleges that Iraqi officials briefed Western intelligence officers before the invasion on the lack of illicit weapons in Iraq.