Retired Gen. İlker Başbuğ was the most prominent defendant among some 250 people facing verdicts after a five-year trial that has become a central drama in tensions between the country’s secular elite and Erdoğan’s Islamic-oriented Justice and Development Party.
The trial has sparked protests, and on Monday police blocked hundreds of demonstrators from reaching the High Criminal Court in Silivri, 25 miles (40 kilometers) west of Istanbul, in a show of solidarity with the defendants.
But Monday’s verdicts were not expected to set off the kind of violent anti-government demonstrations that were recently sparked by a government plan to build a replica Ottoman-era barracks at a park near Istanbul’s central Taksim Square.
In addition to Başbuğ, at least 16 other defendants were sentenced to life in prison, including 10 retired military officers and Doğu Perinçek, the leader of the left-wing and nationalist Workers’ Party. Sixty other defendants received sentences ranging from a year to 47 years, according to state-run TRT television news.
At least 21 people were acquitted.
The defendants were accused of plotting high-profile attacks that prosecutors said were aimed at sowing chaos in Turkey to prepare the way for a military coup. The prosecutions already have helped Erdoğan’s government reshape Turkey’s military and assert civilian control in a country that had seen three military coups since 1960.
The trial, which began in 2008, grew out of an investigation into the seizure of 27 hand grenades at the home of a non-commissioned officer in Istanbul in 2007.
The defendants were accused of being part of an alleged ultra-nationalist and pro-secular gang called Ergenekon, which takes its name from a legendary valley in Central Asia believed to be the ancestral homeland of Turks.
In thousands of pages of indictments, prosecutors maintained that the gang was behind a series of violent acts, including one in 2006 on a courthouse that killed a judge. Prosecutors say that the incidents were made to look as though they were carried out by Islamic militants, in a bid to create turmoil and provoke a military intervention.
Prosecutors say the gang also plotted to kill Erdoğan, Nobel laureate author Orhan Pamuk and other high-profile figures.
The defendants had rejected the accusations, and they were expected to appeal Monday’s verdicts and sentences to the Court of Appeals in Ankara.
Prosecutors demanded life prison terms for 64 of the defendants, mostly on terrorism charges. Others were charged with possession of firearms or merely membership in Ergenekon.
Mehmet Haberal, a surgeon and founder of a university in Ankara, and Mustafa Balbay, the Ankara representative of pro-secular Cumhuriyet newspaper, both faced life prison terms but received sentences of 12 years and 34 years, respectively. The two men were elected to Parliament in 2011 while in prison but were not able to take their seats.
Tuncay Özkan, a prominent journalist who helped organize a series of anti-government protests in 2007, was given a life sentence.
The case has polarized the country between those who see it as an opportunity to unravel a shadowy network of ultra-nationalists known as the “Deep State” that allegedly acted behind the scenes with impunity, and those who believe it is a government attempt to muzzle Erdoğan’s secular-minded foes and undermine Turkey’s secular legacy.
In a separate case, more than 300 military officers, including Turkey’s former air force and navy chiefs, were convicted last year of other plots to bring down the government in 2003 and some were sentenced to 20 years in prison. Those verdicts are being appealed.