In the pre-dawn gloom, through weary villages shaded in gray, the soldiers of the 3rd Battalion, 509th Parachute Infantry Regiment, searched for the enemy. An aerial drone had spotted men burying weapons in a nearby Sunni cemetery.
The soldiers walked along a thin ribbon of sandy road, flanked by tall reeds and palm trees, until they reached this forlorn place covered with crumbling gravestones. Silence mocked the unit, for the men had vanished. Soldiers pried open graves searching for the cache and 15 minutes later found four guns and some ammunition. Lt. Thomas Murphy, 32, wondered who the men had been. Members of al-Qaeda in Iraq? Loyalists of the former government? Tribesmen?
"Here we have so many different enemies," he said.
On the unruly outer fringes of the Sunni area south of Baghdad known as the Triangle of Death, American soldiers navigate more than a dozen battle zones straddling the fault lines of sect and tribe. Al-Qaeda in Iraq -- identified by President Bush and his generals as the main U.S. enemy -- is just one of myriad armed groups competing here for influence and authority. This arid region nourished by the Euphrates River is a microcosm of the many often-overlapping conflicts that have erupted across the new Iraq.
"We're fighting in multiple directions," said Col. Michael Garrett, commander of the 4th Brigade Combat Team (Airborne) of the 25th Infantry Division.
In Garrett's office at Forward Operating Base Kalsu, near the Triangle's southern edge, a large map of his brigade's theater of operations hangs on the wall. South of Kalsu, the land stretches toward the Shiite cities of Musayyib and Karbala. To the northwest, across the farmlands of Jurf al-Sakhr and Khidr, Sunnis are in control. And to the north is Iskandariyah, a volatile mixed-sect town of factories and low-slung buildings.
"We are in the middle of it," Garrett said, indicating the center of his area of operations, which is the size of Rhode Island. "I'm not fighting one sect or the other. I'm fighting both. And not only am I fighting both, but at certain points I have to put my forces in between the Sunni and Shia groups to protect the populace."
Earlier in the day, a roadside bomb had exploded near a convoy of Humvees close to Kalsu. Shiite militias control one side of the road, Sunni insurgents the other. To determine the enemy's identity, Garrett wanted to know what type of bomb it was.
He learned it was an explosively formed penetrator, or EFP, a powerful device that the U.S. military says is used mainly by Shiite militias.
"Shiites don't like to shoot. . . . They just EFP you," said Maj. Craig Whiteside of Silver Spring, Md. "The Sunnis use snipers, RPGs, mortars -- they'll attack you in every possible way," he added, using the abbreviation for rocket-propelled grenades.
Or they'll attack each other. Intra-tribal, intra-Shiite and intra-Sunni clashes play out against a backdrop of byzantine allegiances and arcane codes of conduct.
"We are in the land of the blood feuds," said Maj. Rick Williams, a liaison to tribes in the area. "It's very difficult to tell a tribal fight from a sectarian fight because interests are pretty mixed. You can't just put up a fence."
Here, al-Qaeda in Iraq is neither the largest nor the deadliest opponent. U.S. commanders say foreign fighters working with the predominantly Iraqi group are rare in this region. Commanders estimate that there are as few as 50 hard-core al-Qaeda members, whose activities are mostly restricted to financing attacks in the area.
"They continue to target us, so we continue to target them," Garrett said.
"We blow AQI and Jaish al-Islami up and make them bigger than they are," said Lt. Col. Robert Balcavage, commander of the 1st Battalion, 501st Parachute Infantry Regiment of the 25th Infantry Division, using an abbreviation for al-Qaeda in Iraq and the Arabic name for the Islamic Army, the dominant Sunni insurgent group in the region.
Of the more than 20 soldiers he lost from November through July, Balcavage said, six were killed by Sunni insurgents or in Sunni areas and 11 by Shiite militias or in Shiite areas. Four died in accidents, and another was killed in a mixed area, he said.
At Forward Operating Base Iskan, 10 miles west of Kalsu, Balcavage powered up his laptop. The barrel-chested West Point graduate pulled up a colorful map of his area of operations labeled "The Faultline and You," which he uses in presentations to his soldiers. It depicts a world divided into sectors representing different levels of threat, from different kinds of enemies.
Balcavage clicked on the center of the map. A white text box popped up with an arrow pointing at the base.
"REMEMBER . . . YOU LIVE RIGHT HERE," it read.
On a recent day along what they call Route Cleveland, Balcavage's soldiers were on high alert. Since they began operations here in November, there had been at least six EFP attacks on the two-lane road to Iskandariyah. The convoy of Humvees moved slowly, the drivers avoiding large rocks or concrete blocks where bombs are typically planted.
They cautiously passed what they call the "EFP hot zone," a sprawling apartment complex filled with Mahdi Army militiamen. Larger-than-life images of Sadr, the cleric, were plastered on buildings.
Two minutes later, the convoy entered a Sunni insurgent zone, passing a large Sunni mosque. Two minutes after that, they were back in Shiite territory as they headed into the heart of Iskandariyah to meet Sabah al-Khafaji, a contractor, to discuss some business.
"Before, we were afraid only of Saddam" Hussein, Khafaji said, sitting in his spacious office, its walls adorned with aerial photos of his bus factory and pictures of luxury cars. "Now, there are many sides we're afraid of. If we push on this side, they will kill you. If you poke on that side, they will kill you, and if you poke over there, then they will kill you," he said, pointing south, east and west in turn.
In Iskandariyah, where nearly two-thirds of the population are Shiites, sectarian killings are on the rise, according to U.S. military commanders. Since November, there have been seven police chiefs. The sixth one was murdered last month.
"The police are afraid to do anything," Khafaji said. Tall and regal, with short, silvery hair, he is a prominent Shiite tribal leader whose family has lived here for generations.
On March 26, Balcavage's soldiers responded to fierce street battles between Sunni insurgents and Shiite militias in Iskandariyah's center.
A series of tit-for-tat mosque attacks had put the town on edge. Then Shiite militiamen based in one mosque attacked a Sunni shrine down the street.
As a unit from the 1st Battalion rolled into the battle zone, not far from Khafaji's factory, machine guns and rocket-propelled grenades suddenly targeted them, according to a military report.
"Both sides stopped shooting at each other, and both opened up on our men," Whiteside said. The Americans had to fight their way out.
That battle convinced Khafaji that U.S. forces are vital to preservation of the tenuous power balance. "Now, the Americans are standing in between, sometimes to push on this side and sometimes to push on the other side," he said. "But if the Americans leave, it will be another story."
Fifteen miles to the south, Col. Mohammed al-Mahawili is struggling to control Musayyib. Four months ago, U.S. commanders installed the 32-year-old former Iraqi army officer as the city's police chief. His predecessor was found to have links to the Mahdi Army.
Shiite militias use the town to stage attacks against Americans. A majority of explosively formed penetrator strikes in the area around Kalsu have occurred in Musayyib, Whiteside said.
Mahawili, a tall, energetic Shiite, has escaped six attempts on his life -- one by machine gun, two by sniper fire and two by roadside bombs. A Katyusha rocket struck his police station.
He tries to keep the peace between a confusing array of combatants -- all Shiites, some allied with Iraq's leading political parties -- jockeying for domination with cycles of revenge killings.
Sadr's followers clash with other Shiites and among themselves. Two days earlier, Mahdi Army militiamen had kidnapped a leader of the influential Mowafat tribe, apparently in retaliation for the assassinations of two militia leaders.
"If the Mahdi Army kills the sheik, this will be a big issue," Mahawili said. "The Mowafat will take revenge."
Mahawili has his own concerns. Musayyib's town council is controlled by Sadr loyalists who back the Mahdi Army, he said. The previous week, he had received an official summons to Baghdad. He refused, worried about an ambush.
"Anything can happen," he said. "I can die anytime."
Twenty miles to the northwest, in the lush marshlands of Khidr, U.S. forces face an elusive Sunni foe. Al-Qaeda in Iraq recruits local tribesmen here, and vendettas unfold both among and within the tribes.
Sunni groups launch attacks from Khidr against Shiites farther south and east. Some fighters fleeing a six-month-old security push in Baghdad have sought refuge in the area, U.S. commanders said. And while U.S. forces in many parts of the country are working with tribes that have turned against al-Qaeda in Iraq, loyalties are often fickle in this region.
"Any group you work with can turn on you," said Williams, the tribal liaison, noting that even Iraqi police units have attacked U.S. troops. "That is part of the operating cost."
Unlike in Iskandariyah or Musayyib, U.S. troops seldom patrol in remote, isolated Sunni areas. The rough terrain and the bombs peppering the roads present formidable barriers. Extremists can find havens in villages and farms.
"We haven't seen many of them yet," said Murphy, the lieutenant in the cemetery, referring to al-Qaeda fighters. "They have a great early warning system."
Increasingly, U.S. forces are launching helicopter missions into these areas to learn the terrain and establish a foothold. "It's detective work," said Lt. Col. Valery Keaveny, commander of the 3rd Battalion, 509th Parachute Infantry Regiment.
But even before their mission to Khidr, frustration ran deep among his soldiers, who have spent months chasing a hard-to-define enemy.
"We haven't done anything here. We'll go for 24 hours and we'll see nothing," said Sgt. Josh Claeson, a radio operator, as he waited with nearly 200 soldiers under the glow of an orange moon for helicopters to Khidr. "Our basic mission here is to drive around and get blown up."
At the cemetery the next morning, after the discovery of the weapons cache, a soldier picked up one of the guns and raised it triumphantly. "Hey, we are heroes," he declared, posing for a camera.
By the end of the day, the search would yield a few more weapons, including an antiaircraft machine gun, and commanders would declare the mission a success.