WASHINGTON » Before 10,000 troops marched through central Helmand province to wrest control of a small Afghan town from a few hundred entrenched Taliban fighters, U.S. officials did something more typical of political than military campaigns: They took some polls.

Perhaps no other feature of the offensive under way in and around the town, Marjah, speaks so clearly to its central characteristic: It is a campaign meant to shift perceptions as much as to alter the military balance, crush an enemy army or seize some vital crossroads.

The polling was aimed at understanding what local residents wanted; how they viewed local security; what they thought of the Americans, the Taliban and the foreign jihadis fighting for local control; and what might give them confidence in the central government in Kabul.

Whatever the limitations of this opinion sampling — what is the margin of error when there are whole neighborhoods where it is deadly to knock on doors? — what the commanders learned helped shape the entire campaign. Among other things, those living in the area still harbor some friendly feelings for the Americans, remembering how years ago they built dams in the region, and strongly favor an effort to oust the Taliban.

That gave the military extra confidence as they mounted a counterinsurgency operation that stands out in many ways.

Notably, this was the first time that the Americans took pains to involve the central government of President Hamid Karzai in such a significant operation, let alone a multiphase campaign that included the military, governance and economic stability. Aside from contributing thousands of troops, Karzai and his aides, with significant help from the United States, basically built a government in waiting. The aim is for the Afghan government to carry out programs in education, health and employment as soon as the area is secured, according to a senior U.S. officer.

The size of the onslaught was a departure from past practice, too. The allied force is so large as to be described by one senior U.S. adviser as “;overwhelming to the point of saturation.”;

And the operation was advertised, almost in neon lights, so far in advance and in such detail that there was none of the element of surprise that combat commanders usually prize.

All of those characteristics are explained by the psychological goal of this campaign, a shift of perceptions among the fence-sitters and the fearful among the Afghan people.

Even domestically, the operation is supposed to show Americans that the buildup ordered by President Barack Obama can have swift and positive results. The White House is not declaring victory, though; after Obama was briefed by Gen. Stanley A. McChrystal, his field commander, on Tuesday, the White House press secretary, Robert Gibbs, said only that the campaign was “;highly planned and orchestrated.”;

The project was set in motion six months ago, when McChrystal reported to Obama that the Taliban, despite its relatively light forces, had seized the initiative largely through adroit exploitation of psychological warfare. Insurgent leaders had become more nimble at exploiting even small victories — retelling even their defeats as successes through a propaganda network of radio broadcasts, Web postings and threatening, hand-delivered “;night letters”; to Afghan villages.

The problem was how a foreign army, no matter how much it built up, could drown out the Taliban message and recast the Afghan government and its coalition partners as winners. Combat operations measured by industrial-age standards of captured terrain and enemy dead had to be replaced by another standard adapted to the information era: whether the operation can win the trust of the local people.

“;The biggest thing is in convincing the Afghan people,”; McChrystal said in Istanbul, where he joined Defense Secretary Robert M. Gates to brief NATO allies just before the offensive began.

“;This is all a war of perceptions,”; McChrystal said. “;This is not a physical war in terms of how many people you kill or how much ground you capture, how many bridges you blow up. This is all in the minds of the participants.”;

Senior Pentagon and military officers also point out that the troop ratio reverses several years in which planners sought to capitalize on new technologies and new theories of military reform to fight in both Iraq and Afghanistan with the smallest possible forces. “;The number of the enemy did not drive the equation,”; said one senior U.S. officer involved in the Marjah effort. “;It was a calculation based on how much ground we wanted to cover with a security blanket to reassure the population.”;

The senior officer and other military officials spoke on the condition of anonymity because they were not authorized to speak about the operation.

Although it is a battle for public support, it is by no means a phony war. The bullets, bombs and booby traps are real, putting everyone in the area, including civilians, at real risk.

The leaflets scattered over the region persuaded some of the Taliban to flee in the face of the onslaught, but others dug in and laid down mines.

It was a risk that the commanders accepted, hoping that civilians, at least, would be able to stay relatively safe. They knew that one of the principal dangers to their psychological war would be the anger stirred if civilian casualties were high.

They are hoping the campaign will be short. Officers say the major combat portion of the offensive should be over within a month or so.

Then political and economic development advisers, now standing by, will move in behind the combat force, along with two thousand Afghan police officers.

On Thursday, the British commander of NATO forces in southern Afghanistan, Maj. Gen. Nick Carter, told reporters at the Pentagon that it would take months to judge whether the local residents were satisfied.

“;We probably won't know for about 120 days whether or not the population is entirely convinced by the degree of commitment that their government is showing to them,”; Carter said.