The past two weeks have witnessed the most intensive escalation of attacks on shipping in the Persian Gulf since the so-called tanker war erupted there in the spring.
Since Dec. 3, when the Iraqis resumed their attacks on vessels calling at Iranian ports and terminals, Iraq has issued no fewer than nine claims of successful strikes on ''large naval targets,'' the official Iraqi code word for oil tankers. Five of the hits have been independently confirmed.
The Iraqi escalation, which ended an undeclared seven-week moratorium on attacks, came as no surprise to observers of political and oil market trends in the region.
Iran has had recent success in attracting buyers for its oil by offering substantial discounts and is estimated to be producing rather more than its OPEC quota of 2.3 million barrels a day. Some 1.7 million barrels are reportedly being exported.
(The Organization of Petroleum Exporting Countries opened its semian-nual conference in Geneva Wednesday. One of the key issues is overproduction among the 13 members.)
The increased number of tankers calling at Iran's main oil terminal at Kharg Island increased Iraq's incentive to resume the strikes. This is so not only because of the greater number of tempting targets, but also because of the knowledge that the accumulating revenues would improve Iran's ability to finance its effort in the 51-month-old war.
Iraq had also spent some time and energy during the summer trying to persuade Japan and other countries not to buy from Iran, but these efforts apparently came to nothing.
The lull also coincided with numerous reports that the Arab Gulf states were again extending exploratory feelers in Iran's direction, assessing the prospects for a revived peace initiative.
However, after last month's summit in Kuwait of the Gulf Cooperation Council, it became apparent that no new initiative was in the air because the Iranians had given no signals of increased flexibility.
''The Iraqis were obviously holding back to give peace feelers a chance,'' said one informed source. ''But when they drew a blank, it was only to be expected that Iraq would want to resume the attacks - and to make up for lost time.''
Informed sources say that the Iraqis' strike capability has also been improved recently by the acquisition of an improved version of the French-supplied, sea-skimming Exocet missiles, which have been credited with most of the recent successful hits. France is also reported to have supplied Baghdad with a number of advanced Mirage F1-EQ5 warplanes, which are capable of delivering the missiles at a range greater than that of the Super Etendards Paris has also sent Iraq.
''The Iraqis also seem to be trying to single out tankers approaching Kharg in ballast, when they are more likely to explode than when they're loaded with crude,'' one oil expert noted.
The Iranians have issued frequent warnings that they would do their best to disrupt oil exports from the Arab side of the Gulf if the strikes around Kharg continued. So far, however, only a small Kuwaiti supply vessel, the 1,150-ton Tariq, has been damaged in an attack attributed to Iranian warplanes.
The intensity of the Iraqi campaign clearly increases the pressure on Tehran to hit back at ships on the Arab side, as it has done in the past.
Iran has, however, appeared to be a relucant protagonist in the shipping war: Tehran has yet to issue an official claim or admission that it is responsible for any of the attacks attributed to its warplanes. Apart from Iran's lack of air power, observers believe Tehran's interests are best served by preserving the status quo in Gulf waters. Iran has been able to export its oil, while Iraq has not.
Tehran has also shown some sensitivity in its complicated relations with the Arab Gulf states. Hints of a thaw in recent months could be killed off by a sharp Iranian response to the Iraqi campaign.
The recent six-day drama of the Kuwaiti jet hijacked to Tehran airport also strained Iran's relations with the Gulf Arabs.
The Iraqis have made it clear that the aim of the intensified attacks is to tighten the ''blockade'' they are trying to impose around Iranian ports, especially the terminal at Kharg Island.
Iraqi spokesmen say the goal of the campaign is to ''bring Tehran to its senses'' so that it will respond to peace efforts.
Apart from a brief period of alarm in May and June, when the tanker war first erupted in earnest, the hostilities against Gulf shipping have had remarkably little effect in deterring the movement of oil and goods in the area.
With attacks on tankers happening only sporadically, the market appeared to adjust to a certain level of risk, and there was no problem finding shippers willing to run in and out of Kharg Island. In late summer, claims were running at a rate of only one every week or two.
However, there is some speculation in oil circles now that the latest spate of Iraqi attacks might succeed in making a dent in Iran's oil sales, especially if the rate of strikes is sustained.
In the four days up to Tuesday, the rate of Iraqi claims rose to an unprecedented level of one claim per day. Half were corroborated by independent sources.
Iraqi missiles have scored confirmed hits on three supertankers since Dec. 3: the 386,000-ton Cyprus-registered Minotaur on Dec. 3, the 323,000-ton Bahamas-registered B. T. Investor on Dec. 9, and the 237,000-ton Greek vessel, Ninemia, which was hit twice, on Dec. 15 and 16.
''That's a significant percentage of Iran's oil sales,'' one oil expert remarked.