The decision was more or less expected, and was greeted with mixed feelings by family members and colleagues.

“We will keep working until we get them all back,” Elif Gunay, the daughter of one of the released defendants, wrote on the same messaging application.

But a senior columnist, Aydin Engin, who has been running the newspaper since their arrests, said it would be a struggle for the paper to survive. “It is very difficult to go on” without those “key people,” he said. “For nine months I was trying to take on their responsibilities, but I am 76 and it is very difficult.”

Mr. Atalay in his testimony on Monday accused the government of President Recep Tayyip Erdogan of trying to silence the paper or seize control of it. And he challenged the very premise of the trial. One of the main charges is that he and his colleagues had changed the editorial direction of the newspaper, which, he said bluntly, the court had no business to question.

Cumhuriyet, founded 93 years ago, is the oldest daily newspaper in Turkey, and nearly as old as the republic itself. Run by a foundation, it has a strong reputation of independent reporting, and its reporters and columnists have been in prison many times over the years for breaking government or military taboos.

Turkey was notorious for being the world’s leading jailer of journalists in the 1990s, but for a decade that began in 1998 the country and later Mr. Erdogan’s Justice and Development Party, or AKP, began reforming its ways. By 2008 only one journalist was behind bars.

In July 2008, though, the government accused a shadowy nationalist organization of plotting a coup and began a series of prosecutions that led Turkey once more to authoritarianism and media oppression. That has accelerated since the coup attempt in July 2016.