Walter Lippmann was an astute political philosopher, journalist, and economist. He (rightly) viewed competent journalists as critical to democracy, while ignorant journalists, and ignorance of journalism, was a threat to democracy.
The journalist, Lippman believed, was the interpreter between policymakers and the public. The people had the right to know about policy, but defense policy, in particular but not exclusively, should not be shaped by public opinion.
These views probably motivated Lippmann to engage in the information wars of the time as he went to Europe in 1918 on behalf of the War Department and the State Department. The two agencies, along with the Navy Department, were behind the Committee for Public Information. Lippmann, however, was involved primarily with the foreign section of the CPI, which was run differently, at times diametrically, to how CPI operated within the United States.
Under orders from the War Department, which Lippmann biographer Craufurd Goodwin believes were drafted by Lippmann himself, he goes to Europe. The Secretary of State wrote to General "Blackjack" Pershing that "Captain Walter Lippmann has been commissioned to assist the War Department in the dissemination of propaganda... the vigorous prosecution of his work on behalf of the Inquiry [a project working closely with Wilson's advisor Col. House and the State Department] and the State Department will aid us in the preparation of the material to be used as propaganda."
The modern mind may cringe at the use of propaganda, but then the term was innocuous. It required a qualifier: good, bad, ours, theirs, etc. Contemporary American English dictionaries were only starting to define the word beyond the scientific distribution of seed and plants ("to propagate").
At the time, the European information space was nearly completely shuttered to any news about the United States, whether political or cultural, as a result of a global news cartel. British Reuters, then a different agency than we know now, and the French Havas were disinterested in having knowledge about American policies and society reach get past America's shores. At times, even after America entered the war, news about the U.S. was limited to such useless information like the former U.S. Ambassador to France having eye surgery.
The "propaganda" that Lippmann was involved with would about getting news about the United States out, to allies, neutrals, and adversaries alike. This included not just news stories written by CPI's foreign section, but delivering American wire services. The goal was to have the allied publics better informed of the realities of the day, and of their ally across the Atlantic. This work was done, in the proverbial "last three feet" by Public Affairs Officers.
The PAO was a role and title established by the foreign section that eventually migrated into the State Department. The irony, to some, is that the PAO came about because of State's refusal to do the work. But that is a another story that does not include Lippmann.