The nearly 8-year-old Persian Gulf war between Iran and Iraq is the deadliest conflict since World War II and the first in which chemical weapons, banned after World War I, are known to have been deployed.

The hostilities, triggered by a territorial dispute, erupted Sept. 22, 1980, when Iraqi tanks rumbled across the Iranian border, and, in the years since the two nations have fought massive land battles, traded missile attacks on each other's cities and attacked oil tankers from neutral countries in a war that threatened the world's oil supplies.A U.N. report last week accused Iraq of widespread use of banned chemical weapons in the war - the first proven use of chemical weapons since they were outlawed after World War I.

An estimated 1 million Iraqis and Iranians were killed or wounded in the war, the deadliest since World War II.

The war also featured a return to World War I-style trench warfare with both sides digging in along massive fronts and shelling each other's forces.

Starting in 1981 when Iraqi warplanes attacked four merchant ships from neutral nations plying the Persian Gulf waters, the war spilled over to affect non-belligerent nations using the waterway to ferry oil supplies.

On May 17, 1987, Iraqi warplanes, in an apparent mission to attack an Iranian ship, fired two missiles at the USS Stark in the gulf, killing 37 U.S. servicemen.

Iran two weeks later warned Arab states in the Persian Gulf it would attack them if they put their port facilities at the disposal of U.S. forces, but on July 18, 1987, U.S. warships began escorting Kuwaiti tankers through the area.

On July 3, 1988, the USS Vincennes accidentally fired three missiles at an Iranian Airbus, killing all 290 people aboard.

On July 17, Iran announced its acceptance of U.N. Security Council resolution 598. Nine days later, U.N. Secretary-General Javier Perez de Cuellar began negotiating separately with Iran and Iraq, culminating in his Sunday announcement had agreed to a cease-fire - the date of which will be announced Monday.