Two U.S. Humvees pulled up to a British position outside Basra shortly before dusk today. It was time to play some mind games with the Iraqis.

Scattered across a wide arc about 2,000 yards away, Iraqi soldiers with mortar and machine guns had been moving around between this post on a desolate spot of sand and marsh and the rising lights of Basra more than two miles away. Occasionally they would fire on the British, who would have trouble identifying their positions for return fire.

One of the Humvees, with loudspeakers on its roof and a U.S. psychological operations team inside, parked beside a British Warrior armored personnel carrier. A Special Forces team drove the second Humvee 100 yards further down a dirt track before pulling to the side. That group's equipment included a small surveillance drone and laser devices for identifying targets to strike pilots.

Soon the soft hum of the drone's tiny engine was heard. The model-sized craft passed over the Humvee with the psychological operations team in it, then headed off into the darkness. Then came a thunderous noise from the speaker: the recorded sound of British Challenger tanks, laid down on eight tracks to create the auditory illusion of multiple armored vehicles on the move.

Playing into a slight headwind, the fabricated screech and whirr of tanks would carry to the Iraqi positions. The plan was to startle the Iraqis into bolting and then call in air, tank or artillery fire when their location was exposed. "We want to keep them off-balance and get them moving," said one Special Operations soldier. "Or keep them up all night wondering."

In the standoff at Basra, secrets and lies have been injected into the battle plan to spook a stubborn Iraqi force that in the face of superior firepower has abandoned conventional tactics in favor of guerrilla attacks on British lines.

The Iraqis are lobbing in mortar shells and running before retaliatory artillery pounds their position. They are sending out small teams of men from the besieged city to harass their enemy with potshots. Recently, up to 30 Iraqi soldiers were reported to have floated down a canal on a pontoon boat outside Basra to gather for an advance on British lines, but under a barrage of fire, the Iraqis quickly retreated.

Tanks and artillery fire rend the air at intervals, including a major British barrage of rocket-assisted projectiles this evening. Sporadic machine-gun fire is periodically audible in the distance. At night, flares and tracer fire illuminate sky and sand.

The British are bottling up Basra, slowly squeezing the Iraqis from every position on their perimeter and killing and capturing soldiers in isolated engagements. They are, however, leaving the city itself largely alone. The Iraqis, the bulk of their armor gutted in ditches outside the city, appear unable to launch a major counter-offensive. "This place will go when Baghdad falls," said a British soldier in a Challenger at the front line, before adding the refrain of most of the troops here: "When are you going to do it?"

In this foggy environment, U.S. Special Operations forces have launched a variety of missions. Teams of Green Berets have moved to safe houses, operating within communities in the area where Iraqi militiamen still rule the streets, military sources say. Others roam the night shining red laser dots onto targets so that pilots above them can attack.

Civil Affairs units, specializing in peaceful dealings with the local population, are directing food and water to neighborhoods where local leaders have allied themselves with U.S. and British forces. And psychological operations teams are mingling fact and fiction in an attempt to bamboozle their foe.

British soldiers at the position where the loudspeakers blared tonight, members of the Irish Guards, listened with amusement. "It sounds like a little choo-choo going round and around," said Jonathan Eccles, a Belfast native and a gunner on one of the Warriors here.

On Sunday night, the noise deception worked, members of the psych teams said. The Iraqis moved in significant numbers, and British guns quickly struck.

But on this night, the Iraqis laid low, perhaps wise to the ploy. And the frustration of the soldiers on the ground mounted.

The drone spotted nothing interesting, and when it returned, it landed in a patch of wet marsh, frying the night vision unit on it and damaging a wing. Expected air support did not materialize until after the two American teams were on their way back to base, and by then it was too late for them to laser any targets.

"A bummer," was how one Special Forces officer described the night's work.