According to some accounts, in March/April 1991, Iraqi Deputy Prime Minister Tariq Aziz requested and was granted permission from Sudan's President Umar al-Bashir to move Iraqi chemical weapons to Sudan in order to circumvent their destruction by the UN. Thus, in the Summer of 1991, as UN inspections became inevitable, Iraq was said to have transferred chemical weapons for "safekeeping" in Yemen and Sudan.
In 1993, Iraq was said to have sent additional chemical weapons to Sudan, this time through Iran.
It is claimed that secret contacts between Iraq and Sudan resulted in the emergence of an "Iraqi-Iranian-Sudanese Axis" by the the Spring-Summer of 1995. Providing Sudan with rudimentary chemical warfare capabilities was a major request from Sudanese President Bashir that Saddam Hussein authorized.
The first joint Iraqi-Sudanese WMD project was facilities initially readied for the handling and service of CW munitions and ultimately the production of basic CW agents. At first, the Iraqis sought to exhaust stockpiles of mustard gas they had stored in Sudan since the Gulf War. With a plausible Sudanese source for these munitions -- the Wau facility -- it is claimd that the Iraqis began using chemical munitions in the Fall of 1995, some months before the Wau facility became operational. At first, planes piloted by Iraqis dropped crude chemical munitions around Kadugli and in the Namang mountains in southern Sudan. According to Sudanese opposition sources, witnesses reported that "deaths and injuries occurred among residents" and that "there was a big change in the color of the corpses and of animals and trees." Comparable sightings were reported in Afghanistan and South-East Asia. It was impossible to retrieve samples and more precise details because of the region's remoteness. Intelligence reports identified the agents used as low-quality Mustard taken from an early consignment shipped from Iraq to Sudan immediately after the Gulf War.
Toward the end of 1995, the Iraqi technicians were said to have developed a simple but reliable delivery system for the Mustard Gas produced at Wau. Hence, the Iraqis could stop using their old bombs which were now implicating Baghdad. Instead, the Sudanese introduced crude canisters which they rolled off the back of An-24/An-26 transport aircraft. Most of these canisters missed their targets because of poor coordination between Sudanese ground forces and the aircraft.
Soon after production started in Wau, the Sudanese Armed Forces were reported to have used Mustard Gas canisters against the Sudan People's Liberation Army (SPLA) on at least two occasions in late 1995: The first was at Nimule and the second was at Kuya -- both sites are near Juba, Sudan's southern capital then was defended by tens of thousand of government troops against a tightening siege by the SPLA forces. Since late 1995, there have been several reports alleging the use of chemical weapons in southern Sudan, and with varying degrees of independent corroboration and specificity of technical details. In 1997, several reports of use of Mustard Gas canisters during bombing raids in eastern Sudan, mainly in the Tulushi/Tulus mountains area, were corroborated independently.
In April 1997 the Sudanese National Democratic Group claimed that Iran had airlifted weapons to Khartoum, including heavy and light armaments and quantities of chemical materials for use in the current clashes with the Sudanese opposition. The Group also claimed that a number of Iranian military advisers had also arrived in Sudan to supervise the use of these weapons, which a consignment of lethal chemical weapons.
Khartoum's confidence in its growing chemical warfare capabilities came to light in mid November 1997, when Sudan was reported to have formally threatened Uganda with strikes with chemical weapons if it continued to support the Southern rebels. This warning came despite Kampala's previous denials of cooperation with the Sudanese rebels and Khartoum's adamant denials of CW capabilities or use.