BALAD, Iraq — In one 24-hour stretch, America's successes and difficulties in this country showed themselves in the figure of Lt. Col. Nate Sassaman.

On Friday, Sassaman stood before the newly elected Balad City Council, walking them through such democratic bedrocks as the secret ballot and the open meeting.

On Saturday morning, after a couple of hours' sleep, Sassaman led a company of 150 soldiers on a series of house-to-house searches for weapons and guerrillas on the outskirts of town.

"It's like Jekyll and Hyde out here," said Sassaman, a 40-year-old battalion commander and former starting quarterback for Army's football team. "By day, we're putting on a happy face. By night, we are hunting down and killing our enemies."

That type of discrepancy is true across Iraq, but seldom is it lived with such intensity in the same place, by the same soldiers, as here to the north of Baghdad.

Six months since President Bush declared the end of major hostilities in Iraq, America's soldiers are waging two starkly different campaigns: laying the groundwork for democratic rule while battling an insurgency that is undermining that very work.

Here in Balad, a district of 180,000 people 50 miles north of Baghdad, the two American campaigns are unfolding side-by-side, by virtue of the area's exceptional demography: The city of Balad is an island of Shiite Islam in the heart of the area known as the Sunni Triangle.

The Shiites in Balad suffered under Saddam Hussein, as they did in the rest of Iraq. For that reason, they have largely been cooperating with American efforts to implant the rudiments of a democratic system. In Balad and in southern Iraq, where the Shiites predominate, the environment remains relatively calm.

But here in central Iraq, American soldiers are battling a ferocious guerrilla insurgency, drawn largely from the region's Sunni population. The Sunnis, though a minority in Iraq, fared well during Saddam's reign, and their neighborhoods are now generating violence against the Americans.

Across much of the area, building democracy has taken a back seat to fighting the war.

So it is that Balad and its environs contain most of the contradictions facing the Americans in Iraq: the relative peace of the Shiite areas and the violence of the Sunni areas, all in one. It is that dual reality that gives Sassaman sleepless nights.

"We're doing something worthwhile here," Sassaman said in an interview at the headquarters of his unit, the 1st Battalion, 8th Infantry, part of the 4th Infantry Division. "But it's clear that our enemies are going to keep attacking us until we kill and capture every one of them. That's going to take a while."