Original sentence: During this phase of the war, the Iraqis used poison gas to repel Iranian attacks.Five days later, Iraqi armed forces began a land and air offensive against Iran.It strained the political and social life of both countries, led to severe economic dislocation and altered the course of Iraqi and Iranian history.Mustard  and nerve gases were used, demonstrating Iraqi ability to manufacture and deploy such weapons.On 17 September 1980, Saddam Hussein announced that he was ending the treaty with Iran which had been signed in 1975.The Iran–Iraq war lasted for nearly eight years and included religious schisms, border disputes and political differences
Edited sentence: Both mustard gas and the more modern nerve gas were used, demonstrating the Iraqis' capability to manufacture and deploy such weapons of mass destruction.Five days later, on 22 September, Iraqi armed forces began a massive offensive against Iran, invading the country via air and land.It strained the political and social life of both countries, led to severe economic dislocation, and permanently altered the course of Iraqi and Iranian history.It was during this phase of the war that the Iraqis made use of poison gas to repel Iranian attacks.It was multifaceted and included religious schisms, border disputes, and political differences.On 17 September 1980, Saddam Hussein announced that he was ending the treaty with Iran that had been agreed in 1975.The Iran–Iraq war lasted for nearly eight years.The role of the United States in the war was very important, in that the United States supplied Iraq with weapons to use against Iran