Hi Barry,
During the Gulf War, Iran and Iraq were at each others throats because Iraq had layed claim to the upper regions of the Shatt al Arab and invaded Khorramshah (I believe.) All out war then ensued. The Shatt al Arab was always a bug-bear in both countries sides.They had a tentative agreement and pilotage from seaward upto Fao/Abadan was by Iraqi pilots,once there any vessels going further up river to Irani ports would be piloted by Irani pilots.Those going to Basrah etc would continue with Iraqi pilots ofcourse.Once the war got into full swing all hell broke loose and Iran were reduced to sending children into battle equipped with a key that would guarantee immediate entrance into the 7th Heaven should they be killed and thus martyrised. I dont know why the Irani forces decided to attack shipping that were using Saudi/Kuwaiti ports unless they thought those countries were siding with Iraq and helping Iraq divert some of it`s oil through their facilities.
What typically would happen would be a small single engine plane would fly over the shipping using the trade routes and if they recognized a particular ship,or one they thought might have been engaged in this trade, they would radio this info to Irani warships hiding over the horizon who would then send a surface to surface missile over and BOOM....here we go again. Inevitably this plane was called the "Angel of Death" and the mere sound of a light engine would have everybody scanning the skyline for possible sightings and thereby a degree of warning could hope to be gained. Not very effective defence I am sad to say.
It did wonders for Dubai Dry Dock shareholders not to mention hordes of salvors.
Jim