AMMAN, Jordan — Iranian troops crossed a key waterway in southern Iraq on Monday, apparently marking the start of a long-expected Iranian offensive that could be the decisive battle in the five-year-old Iran-Iraq War.
A statement issued Monday night in Tehran said that Iranian forces seized a "wide area of sensitive and strategic regions" west of the Shatt al Arab waterway and that the territory remained under Iranian control.
Iraq said that its forces were counterattacking along a broad front near Basra, an Iraqi city at the northern end of the Persian Gulf. But a Baghdad communique acknowledged that the Iranians have gained "a shaky foothold in some forward areas" of Iraqi territory.
There was no independent confirmation of either side's report.
Western military analysts, speaking by telephone from Baghdad, said the Iranian assault appeared to be the first wave of an expected major Iranian offensive. The late winter is favored by the Iranians for attacks because rainfall leaves the region of southern Iraq a quagmire that makes it difficult for the Iraqis to use their tank superiority to full advantage.
According to the analysts, the Iranians have massed 250,000 men on the southern war front for several weeks. The apparent Iranian goal is to threaten to cut off Basra, Iraq's second-largest city, from the rest of the country, which could destabilize the regime of Iraqi President Saddam Hussein.
The war in the oil-producing Persian Gulf region has been one of the most lethal conflicts of the modern era, with an estimated half a million casualties to date. During an offensive last year, Iran lost an estimated 30,000 in one week, while Iraqi deaths were placed at 10,000.
In addition, Western diplomats said that both sides are now fully equipped to use poison gas on a large scale. Iraq has used mustard gas in the past but in limited quantities. The two countries have also developed anti-gas defenses, and the use of gas is widely expected in the current campaign.
Although the Iranian offense was turned back last year, the diplomats said that the Iranians appear to be far better prepared for the Iraqis now and that the battle could be a close call for either side.
Drive Through Marshes
According to the war communiques, the Iranians appeared to have attacked on two fronts through the Hawizah marshes beginning Sunday night. The date is significant, since it is the eve of the seventh anniversary of the Islamic revolution that toppled Shah Mohammed Reza Pahlavi and brought the Ayatollah Ruhollah Khomeini to power.
An Iranian communique said that Iranian forces captured an island called Umm al Rasas, which it said is situated west of the Shatt al Arab. The statement said that the island contains important Iraqi oil installations.
"Basra has sustained considerable damage, and a large number of enemy soldiers have been routed and a considerable number have been captured by the forces of Islam," Tehran radio said. "Areas that have been conquered and the booty obtained are sizable."
Baghdad radio, quoting a report by the state news agency, said that the Iranians paid a "dear price" in the assault and that Iraqi forces are pursuing the survivors. The correspondent said that bodies of the dead Iranian soldiers are floating in the waterway.
"Birds of prey, follow us to the battlefield," the Iraqi broadcast said. "With God's help, the frustrated and treacherous enemy will face the fate we have come to expect for it."
After last year's defeat, the Iranians built three roads into the marshes and began fortifying the islands there. They appear to have established artillery emplacements to provide cover for the offensive, as well as using the islands as jumping-off points for reinforcements and heavy equipment. The Iranians cross the marshes in hundreds of speedboats purchased from Japan.
The Iranians actually severed the main north-south Iraqi highway during the fighting last year, but were equipped with only personal weapons. Iraq, which holds a 5-to-1 superiority in tanks and a 6-to-1 edge in planes, was able to crush the advance before the Iranians dug in.
According to Western experts, the Iraqi strategy appears to be aimed at allowing the Iranians to make initial advances, perhaps even across the Tigris River onto high, dry ground where the huge Iraqi armor corps can be unleashed. Iraq has just received 300 new T-72 attack tanks from the Soviet Union.
Iraqi officials have been telling Western diplomats in Baghdad that they have acquired a major new secret weapon that they will deploy against Iran in the event of an emergency. The diplomats said it is unclear whether Iraq has obtained a new weapons system, such as surface-to-surface missiles from the Soviets, their primary arms supplier.
Iran has been suffering under almost daily air attacks by Iraqi planes, which now range freely over the gulf. Since Jan. 1, the Iraqis have flown 2,500 combat missions, sharply curtailing Iran's oil production.
To mark the anniversary of the Iranian revolution, the 85-year-old Khomeini made a rare public appearance in Tehran.
Speaking to foreign Muslims, he noted widespread demands for conciliation, saying that today "there is no government that would not like Iran to show some flexibility toward it, and that is true for the United States, the Soviet Union and France. They are the ones who are isolated."
Iran has had trouble getting a regular arms supplier because the United States has embargoed arms sales since the Tehran hostage crisis, and the Soviets are Iraq's principal ally.
Western diplomats said that some arms shipments are coming to Iran from China while others are reaching it by way of Syria and Libya.