Police escorted retired Gen. Ismail Hakki Karadayi, 80, from his Istanbul residence to the capital, Ankara, to testify before the prosecutor who is leading an investigation into a 1997 military campaign that forced former Prime Minister Necmettin Erbakan to resign.
Several other officers have already been charged in Erbakan's ouster, which has since been dubbed Turkey's "post-modern coup" because unlike previous coups, the military did not grab power through the use of tanks and soldiers and the government was replaced by another coalition.
Turkey's military, which has seen its duty as protecting the country's secular traditions, had previously staged three other coups. Prime Minister Recep Tayyip Erdogan—whose ruling party splintered from Erbakan's now-shuttered Welfare Party and came to power in 2002—has curbed the power of the generals and vowed to bury the military's influence in politics for good.
"As Turkey is normalizing and advancing toward a stronger democracy, one cannot expect it not to force (the perpetrators) of undemocratic and unlawful acts to account for their actions," said Mehmet Ali Sahin, the deputy head of Erdogan's Justice and Democracy Party.
The two ailing leaders of the country's 1980 military are already on trial for the takeover that stopped deadly fighting between political extremists but also led to a wave of executions and torture.
In September, a court in Istanbul convicted nearly 330 army officers, including the former air force and navy chiefs, of plotting to bring down Erdogan's government in 2003 and sentenced some to 20 years in prison. The case, however, has been marred by procedural flaws and long pre-trial detention periods. All of the defendants are appealing the verdict.
Hundreds of other people are on trial separately charged with conspiring against the government.
Turkey's main secular opposition party insists the defendants are not getting a fair trial and dozens of supporters gathered outside the courthouse Thursday in support of Karadayi. Lawmaker Aylin Nazliaka said Erdogan's government was using the judiciary "as if it is seeking revenge" against the military.
Karadayi's questioning followed testimony by some of the former officers charged in Erbakan's ouster, who claimed they had acted within the military's chain of command, according to the state-run Anadolu news agency.
Karadayi served as the chief of the military staff from 1994 to 1998, when the military pressured Erbakan to resign over his alleged attempts to raise the profile of Islam in the predominantly Muslim but secular country, including attempts to allow civil servants to wear Islamic-style clothing and to change work hours to suit religious fasting.
On Feb. 28, 1997, the military-dominated National Security Council threatened action if Erbakan did not back down. He resigned four months later.