Frans van Anraat was living openly under his own name when he was arrested in an Amsterdam suburb in late 2004, after an international investigation.
The Iraqi regime used chemical bombs in a number of attacks
Now 63, he has become the first man convicted in connection with alleged war crimes committed against Kurds in Iraq and Iran.
Van Anraat was convicted of complicity in war crimes but cleared of genocide.
He arrived home in the Netherlands in 2003, ending decades of involvement with Saddam Hussein's regime in Iraq.
Previously, he had fled from Italy to Iraq in 1989.
His relationship with the deposed Iraqi leader led Dutch prosecutors to accuse him of directly supplying thousands of tons of base materials for chemical weapons used in the 1980s.
The United Nations suspected van Anraat was a major chemical supplier to the regime.
Some of those chemicals were allegedly used in the 1988 bombing of Halabja in northern Iraq, which killed an estimated 5,000 civilians in a single day.
The attack on the mainly Kurdish town was part of Saddam Hussein's wider campaign against the Kurds and was one of his worst atrocities.
Van Anraat will now serve 15 years in prison for his role in the supply chain.
Chemical weapons were also used by the Iraqi army against Iranian forces in their 1980-1988 war.
Van Anraat, dubbed "Chemical Frans", did not deny supplying the chemicals, but says he did not know what they were to be used for.
In a 2003 interview with Dutch television program Netwerk, van Anraat said: "This was not my main business, this was something I did in passing," the Associated Press news agency quoted him as saying.
"Somewhere once back then, I got the request whether I could deliver certain products to them, which they needed," he said.
"And because I had a very good relationship with the [Iraqi] oil ministry, and that's where the request came from, I tried to see if I could do it. And that was successful and we did deliver some materials."
However, prosecutors alleged that van Anraat was aware of the final purpose for the materials he supplied.
"From different sources it can be deduced that the suspect was aware of the destination and the final purpose for the base materials supplied by him," the prosecutor's office told the AFP news agency.
Thousands of people died in the bombing of Halabja
Among the chemicals van Anraat was accused of supplying was thiodiglycol, a chemical solvent used in the textile industry and in the manufacture of mustard gas.
He was found guilty of arranging 36 shipments - a total of 538 tons - from the US via the Belgian port of Antwerp, through Aqaba in Jordan to Iraq.
Prosecutors said van Anraat had been a suspect since 1989, when he was arrested in Milan at the request of the US Government.
He was released pending a decision on his extradition, and fled to Iraq, where he remained until 2003.
After the US-led invasion of Iraq in March 2003, he returned to the Netherlands.
Media reports suggest his bags were packed when Dutch police entered his home to arrest him in December 2004.
He was thought to be the first Dutchman to face genocide charges, but was cleared on those counts, despite the court ruling that the chemical attack on the Kurds was genocide.