Inside the security-police headquarters in Riga, Latvia, not much appears to have changed since the end of the Cold War, nearly three decades ago. A long, beige hallway leads to the executive conference room, which is furnished with an overstuffed couch, a giant television, and a patterned tea set atop a credenza.

The security police, like the F.B.I. in the United States, conduct counterintelligence, which mainly involves trying to uncover and stop Russian interference in the nation’s affairs. Ever since Latvia regained its independence, in 1991, after the breakup of the Soviet Union, Russia has used spies, Latvian turncoats, blackmail, bribery, surveillance, and other skullduggery to stir up trouble, Normunds Mežviets, the director-general of the security police, told me during an interview. For at least ten years, Russia has also employed the Web to spread disinformation about Latvian society, in an effort to weaken citizens’ support for European unity and for their democratic form of government, he said.

Despite the headquarters’ décor, much has changed there, as I discovered when I visited, this spring, while reporting a story for the Washington Post on how Europe is handling Russian disinformation. To fight online troublemaking, Mežviets and his officers have become experts in the business of the news media. They know the owners and journalists of prominent television stations and newspapers. They also make it their business to know even the tiniest and most amateur Russian-language Web sites that pop up in the Latvian news sphere. When the officers spot even a discreet change in the Russian-language sites, they investigate those, too. By now, Mežviets has learned so much about the media that sometimes he sounds more like a journalism professor than a national-security officer. “It’s very important that normal media use really credible sources,” he told me in his office.

He recently lobbied Latvia’s legislature to adopt a law requiring that the government approve the sale of major media companies, so that they never fall under the control of foreign foes. Foreign-owned private-equity firms, whose goal is often to flip lacklustre companies after making them profitable, already own large mobile-phone and cable companies in the country. With a population of only 1.9 million, Latvia views a media grab by, say, Kremlin-friendly oligarchs as a major security threat. Mežviets said that, since there are “only three Latvian TV channels,” if one were to fall into Russian-friendly hands, “that could have a real impact.”

For Mežviets, Latvia’s news media is just as important as the country’s energy supply. If Russia were to impede the flow of natural gas to the Baltic nations, their economies would tumble, which is the reason that Lithuania built a floating liquefied-natural-gas terminal off its coast, in 2014, and recently signed its first deal to buy natural gas from the United States. Similarly, Mežviets argued, if Russia could impede the flow of professional journalism with fabrications about Latvian institutions, soon people would turn against the government as they did against the Soviets. “The media are a strategic asset, just like oil and gas,” Mežviets has concluded.

Viewing the professional media as a strategic asset, the pipeline through which credible information travels, had never occurred to me in my thirty-five years as a reporter. But it is certainly the view of authoritarian governments and those transitioning to authoritarianism. The Chinese Communist Party maintains political power in part by controlling the information that citizens read, hear, and watch, and by imprisoning journalists whose work challenges the political status quo. The Russian President Vladimir Putin suffocated independent television and then built up a vast new state-run cultural, entertainment, and news apparatus to substitute as the main pipeline through which most Russians are informed about their neighbors and country.

In every nation on Earth where the government is moving from a participatory to an authoritarian form of rule, seizing the information pipeline is a prerequisite for staying in power. The general turned President Abdel Fattah El-Sisi did it in Egypt, by imprisoning dozens of journalists and censoring news about the military not provided by his own government. President Recep Erdoğan’s Turkish prisons now hold nearly one-third of all the journalists imprisoned in the world. “The people that claim to be journalists are not there because of their work as journalists but because of their links to terrorism,” an officer at the Turkish Embassy said recently.

The pattern is the same in Saudi Arabia, Iran, Sudan, and Ethiopia, among other nations. As a strategic asset, the media in these countries serve the national interests as defined by their rulers. Thus, the kings and princes of the Gulf states demanded that Qatar close its groundbreaking Al Jazeera network, and the monarchy in Bahrain recently shut down Al-Wasat, the only independent newspaper left in the kingdom. “The year 2017 could be remember by historians as the year of backsliding on freedom of expression, pluralism and human rights,” Al-Wasat’s crestfallen editor-in-chief, Mansoor Al-Jamri, told me in an e-mail, three weeks after he had to let a hundred and eighty-five staffers go. “Many governments were emboldened by this anti-democratic trend and took the opportunity to crackdown.”

In most of Europe, where hoax news stories and Web sites with bogus articles are muddying the digital pipeline of reliable information, political leaders have publicly reaffirmed their faith in the mainstream media and urged them to do a better job exposing imposters. With the help of journalists and researchers, the European Union’s East Stratcom Task Force has published thousands of examples of false or twisted stories in its weekly Disinformation Review.), available in eighteen languages.

Reporters and researchers in Britain, France, Germany, the Czech Republic, the Netherlands, Switzerland, Finland, Sweden, Ukraine, Latvia, and Slovakia maintain lists of phony sites, and have helped readers follow the trail of conspiracies as they work their way through Twitter and Facebook. In France, after the last-minute leak of thousands of hacked documents from the Presidential candidate Emmanuel Macron’s campaign, the French election commission appealed to the media and citizens on social media “to show a spirit of responsibility and not relay the contents, in order not to alter the sincerity of the ballot.” Most complied.

Le Monde told readers that it wouldn’t publish the documents because they were too voluminous to verify in the forty-eight hours before the vote, and because the candidates would not have time to respond, as required under French law.

Should professional journalism in the United States be considered a strategic asset, too? Perhaps that is why the Founders gave the unkempt, sometimes inaccurate news industry special protections against government interference, under the First Amendment. And why the Supreme Court’s messy 1971 Pentagon Papers decision sided with the media against prior government censorship, even when there’s a chance that a news outlet could be publishing information that damages national security.

Michael V. Hayden, a retired U.S. Air Force general and the former head of both the C.I.A. and the National Security Agency, was deeply critical of the reporting that the New York Times journalist James Risen did on the N.S.A.’s warrantless wiretapping, and of the articles that I wrote on the C.I.A.’s secret prison. But he told “60 Minutes” that he thought Risen, facing jail time for refusing to name his source, should not be imprisoned. As for my reporting, he said in an interview, “I hammered your collection [of information] because you suborned my employees. You hammered me because we [at the C.I.A.] hurt some people. I argue with you tactically but not strategically. The First Amendment protects me, too.”

“Somebody has to be the protector of objective truth,” Robert J. Giesler, the former director of information operations and strategic studies in the office of the Secretary of Defense and a longtime student of information warfare, told me—and that protector can’t be the government. “Quite frankly, it’s the single most important function of journalism that can’t be filled by anyone else.”