From a hastily scooped trench here amid the Iraqi Army front lines today, the provincial capital of Ahwaz is lost somewhere up the road in the shimmering mirages that continuously blur the vast, flat plain that is Iran's Khuzestan Province.

As far as the eye can see on either side of the two-lane, blacktop road from the besieged river port of Khorramshahr to the south, a vast army is dug in at this milepost about 14 miles south of Ahwaz. Hundreds of Soviet-made T55 tanks are deployed behind protective embankments of bulldozed earth.

To the rear, a line of 130mm cannons, their long muzzles pointing into the hazy blue sky, spew orange flames and smoke as they lob their shells north. Everywhere it seems, there are transports, supply trucks, armored personnel carriers and antiaircraft guns to protect them.

It is an impressive sight. But there is only one thing wrong. According to the communique in Baghdad, the Army should not be there at all. Ahwaz, Iraq has claimed, fell to the advancing Iraqi Army three days ago.

Huddling in a trench under Army orders to stay down because of earlier incoming Iranian artillery fire, it is clear that, like in so many other wars, the official claims have little to do with reality.

Officers here tell visitors to the front that, of course advance forces are in fact already inside Ahwaz. But the defensive positions here, the nervous mood of the troops, the highly accurate incoming artillery fire and the sporadic attacks by Iranian Phantom jets that drop their bombs with impunity, indicate that the Iraqi Army is still far from capturing its much-advertised objective.

In fact, despite the rapid advance to occupy about 1,000 square miles of provincial wasteland, the Iraqis appear to be bogged down here just as they are in the south around Khorramshahr and the adjoining oil refinery complex at Abadan.

Senior officers refuse to discuss the reasons why their Army is still far south of the city that their government already has claimed is taken.

"We cannot talk," said one colonel. "We are busy with operations."

During an hour and a half among the Iraqi forces at the Ahwaz front, the only operation evident was the troops' efforts to tuck in deeper to avoid the random Phantom jet that swooped over their positions dropping bombs.

One jet destroyed an Army truck moving up the highway two miles to the south. A second jet knocked out an ammunition truck less than a mile away and dropped a second bomb among the artillery emplacements.

As in most previous engagements witnessed along the Iraqi front in Khuzestan since the war began last week, the Phantoms were challenged by nothing bigger than manually operated field antiaircraft guns, a weapon that can only down a fast moving jet by luck. There were no Iraqi Air Force jets in the sky over this huge army to contest the Phantoms. And there were no surface-to-air missiles evident.

"Our Army's machine guns are enough to down the Iranian Jets," said an Iraqi escort officer. "We are saving our jets to destroy Persian electric, water and military equipment."

There was no evidence of wreckage to substantiate the captain's claims.

In fact, driving to the front along the line from the west used by the Iraqi Army to capture the Khorram-shar-Ahwaz road here, there is little evidence that any real combat has taken place. The only sign is from a long-distance duel between Iraqi guns here and the Iranian artillery, which is believed to be set up behind Ahwaz in the highly defensible foothills of the Zagros Mountains.

The Kuzestan plain that flows into eastern Iraq without a blemish to break its monotonous flatness is clearly almost indefensible. The border from which Iraq began its 72-mile drive to its present positions here is nothing but a dried-out irrigation canal.

The only Iranian positions between the border and here were three tiny, turreted forts used by Iranian police and border patrols. In between there is nothing but a vast, empty wasteland of desert tundra and dusty tracks.

Although all three of the tiny forts have been holed by shell fire, there is little evidence that fight actually took place at any of them. There are no damaged vehicles, no empty shell cases, and except for one bloodied khaki shirt, no sign of casualties.

In a four-hour drive through this bleak corridor of occupied Iran, there was evidence of destroyed or captured Iranian vehicles or damaged Iraqi equipment.

Rather than standing and fighting on a terrain both worthless and devoid of natural defense positions, the Iranian Army appears to have staged a well-managed retreat to Ahwaz and the hills behind the city, where presumably they are in a much stronger position to counter the Iraqi thrust.

Iraq's much vaunted week-long thrust into Iran has been an advance in which the only real enemies were heat, dust and thirst.

So far the war between the two oil-producing nations has been an air war against each other's vital oil industries and distant artillery duels between fixed positions. But with the Iraq Army now facing the Iranian forces south of Ahwaz, there is evidence that the real, and perhaps decisive, war on the ground may now be about to begin.