[This is part of a week-long series on CBC radio's Ideas about the First World War, which started almost exactly 100 years ago when the heir to the Austrian throne was assassinated in Sarajevo. Listen to Ira Basen's full documentary about World War One and its connections to modern marketing on June 24 at 9:05 p.m. Eastern on CBC Radio 1's Ideas.]

Corporations spend billions each year trying to influence how people think, act and spend. But the fields of modern public relations and product marketing really aren't all that new – they got their big start in a broken campaign promise made nearly 100 years ago.

And as broken campaign promises go, this was one of the biggest.

In April 1917, the First World War had been raging for almost three years, but the United States had remained outside the fray. Although supportive of the Allied Powers, President Woodrow Wilson urged Americans to be neutral in thought and action. Public opinion in the U.S. was solidly behind him - Wilson had been re-elected in November 1916 on the slogan "he kept us out of war."

Five months later, the president had a change of heart.

Germany was continuing to harass American shipping, and there were real concerns in Washington that the war would be lost. So on April 6, Wilson was able to persuade Congress to declare war on the Central Powers.

Persuading Americans to support the war would be a more challenging task.

Committee on Public Information

Within days of the declaration, the president authorized the creation of the Committee on Public Information.

Under the leadership of George Creel, a former muckraking journalist, the CPI was tasked with winning the war at home by firing up a reluctant American population into what Creel called "the white hot mass of patriotism," and spreading the good news about America and its democratic values throughout the world.

The famous World War One "Uncle Sam" recruitment poster was painted by James Montgomery Flagg for the Committee on Public Information. (Reuters)

The CPI brought together many of the brightest minds in advertising, journalism, graphic design, academia, and a relatively new industry called public relations.

By the end of the war, more than 100,000 Americans had contributed to the CPI's efforts. They created Uncle Sam and other iconic recruiting images. They churned out millions of press releases, bulletins, photographs and posters, and produced silent movies with names like Pershing's Crusaders and America's Answer.

And 75,000 local notables, known as Four Minute Men, signed up to deliver carefully crafted four minute inspirational orations in church halls, movie theatres, and anywhere else that Americans gathered.

It all worked spectacularly well.

Within months, Americans had shed their initial war reluctance. Young men were flocking to recruiting offices, and millions were giving money to support the "Liberty Loan" program to help finance the war effort.

The success of the CPI opened the eyes of many of its publicists to new techniques of mass persuasion, and brought the fledgling public relations industry from the fringes of American commerce into the mainstream.

Heart vs. head

"Our effort was educational and informative throughout," George Creel insisted after the war.

In fact, it was anything but.

The CPI was the largest propaganda machine the world had ever seen. And while its title stressed "information," the Committee's publicists understood that electrifying American public opinion would take an appeal to the emotions, not the intellect.

The CPI's Division of Advertising churned out posters and ads that depicted German atrocities that never happened, played up threats to American homes and families that were wildly exaggerated, and generally appealed to the fears and anxieties that lurked beneath the surface of public consciousness.

All of this was observed with great interest by a young member of the CPI team named Edward Bernays.

In this Sept. 26, 1918 photo, a U.S .Army 37mm gun crew man their position during the World War One Meuse-Argonne Allied offensive in France. The CPI’s Division of Advertising churned out propaganda to bolster the support of Americans at home for the war effort. (The Associated Press)

When the war broke out, Bernays was hired to write propaganda for the CPI's Latin American section. He was a 26-year-old publicist based in New York City, and he had very big ambitions.

Bernays was the nephew of Sigmund Freud and he shared his uncle's fascination with the unconscious mind. But while Freud sought to liberate people from their subconscious drives and desires, Bernays wanted to harness those passions for commercial ends.

His work with the CPI had convinced him that if you could sell war by appealing to images and symbols, then you could do the same thing to sell just about anything.

"I decided that if you could use propaganda for war, you could certainly use it for peace," he told a BBC interviewer in the early 1990s.

Bernays had concluded that public opinion was fundamentally irrational, and irrationality was now the filter through which human nature could best be understood. Symbols, not facts, would be the primary tool of persuasion. Public opinion was to be manufactured and managed through communications strategies that aimed for the gut rather than the brain.

Torches of Freedom

Bernays returned to New York after the war and set himself up as a "counsel on public relations," determined to put his theories into action.

One of his earliest successes was for the American Tobacco Company. It had hired Bernays to figure out a way to get American women to feel comfortable about smoking in public.

After consulting a colleague of his uncle's, Bernays concluded that women needed to see cigarettes as "torches of freedom" that would help emancipate them from the social taboos imposed on them by men.

He arranged for several young women to walk down 5th Ave. in New York during the Easter parade, smoking.

As Bernays expected, the story made front page news across the country, and the rest, unfortunately, is history.

Regimenting the public mind

Bernays, who died in 1995 at the age of 103, is widely regarded as one of the founding fathers of modern public relations.

Writing 10 years after the war, Bernays noted that World War One had, 'opened the eyes of the intelligent few in all departments of life to the possibilities of regimenting the public mind.'

For good and ill, the influence of Bernays can be felt throughout the world of public relations today. He was among the first to do research into what consumers actually want, one of the first to understand the value of "expert" testimonials in advertising, and to capitalize on the power of "front groups" that allow organizations to anonymously advocate for their causes.

Throughout his life, he insisted that the "astounding success" of the CPI's propaganda was the key to the evolution of public relations.

Writing 10 years after the war, Bernays noted that the First World War had "opened the eyes of the intelligent few in all departments of life to the possibilities of regimenting the public mind."

They had seen public opinion moulded in ways they had not previously imagined. They had learned the power of images and symbols, they had begun to explore the subconscious triggers that could activate public passions.

These were lessons they didn't soon forget when the shooting stopped.