Turkish President Recep Tayyip Erdogan addresses a labor union meeting in Ankara on Dec. 3. (Murat Cetinmuhurdar/Presidential Press Service Pool via Associated Press)

IN 2012, the Committee to Protect Journalists issued an alarming report about press freedom in Turkey, documenting “widespread criminal prosecution and jailing of journalists,” the “government’s use of various forms of pressure to engender self-censorship,” and “a harsh anti-press tone set at the highest levels of government.” The report warned, “Turkey’s press freedom situation has reached a crisis point.” But since then, conditions have only deteriorated.

The latest evidence that President Recep Tayyip Erdogan is trying to silence the media came Nov. 26 when two prominent journalists were detained. Can Dundar, editor in chief of the newspaper Cumhuriyet, and Erdem Gul, the paper’s Ankara correspondent, were accused of aiding an armed group and of espionage, charges that reflect Mr. Erdogan’s fury at the newspaper’s reporting.

His anger was sparked by a report May 29, just before an election, when Cumhuriyet published video on its website showing gendarmerie and police officers opening crates on the back of trucks. The newspaper said the cargo contained heavy weapons and ammunition bound for Syrian rebels and was sent by Turkey’s national intelligence agency, the MIT. The video dated from January 2014. The government had initially denied the trucks were carrying arms and said it was humanitarian aid; later, the government said the trucks may have been carrying arms destined for Turkmen kinsmen in Syria.

Mr. Erdogan’s furious reaction suggests the newspaper exposed an inconvenient truth. Two days after the footage was revealed, Mr. Erdogan declared the newspaper had committed “slander” against the intelligence agency and “an act of espionage.” He vowed that Mr. Dundar would “pay a heavy price for this” and asked that he be jailed for life. The next day, scores of Cumhuriyet editors and columnists insisted on the front page of the newspaper that they were all responsible and began a social media campaign saying that “Can Dundar is not alone.” Mr. Erdogan responded by filing an individual criminal complaint against the paper and its editor. His determined effort to punish them led to a Nov. 26 court decision ordering the two journalists to be jailed pending trial. The pair have addressed a letter to the leaders of the European Union, saying they are in prison for “defending the public’s right for information.”

The Cumhuriyet editors are hardly alone. Dozens of journalists have been jailed in recent years. In October, eight international press freedom groups conducted an “emergency” inquiry in Turkey and concluded that “pressure on journalists operating in Turkey has severely escalated” this year. They found cases of physical attacks on journalists, raids on media outlets, threatening rhetoric, increasing use of slander and anti-terrorism laws to target the media, ongoing imprisonment of journalists and deportations of foreign correspondents.

All of it has been driven by Mr. Erdogan’s singular thirst for power, which includes a plan to revise the constitution to enshrine him as supreme chief executive. On his path to autocracy, Mr. Erdogan is pounding a once-vibrant media into lifelessness — and with it Turkey’s democracy.