More than 300 soldiers, including acting and retired senior military commanders, were found guilty on Friday of plotting to overthrow the Turkish government.
CNN reported that 333 of the 365 suspects were sentenced to up to two decades behind bars.
The three generals, Çetin Dogan, a former first army commander, Ibrahim Firtina, a former air force commander and Ozden Ornek, a former naval force commander admiral, would only serve 20 years in prison for their bid to overthrow Turkey's government, Al Jazeera reported.
The Associated Press noted that the panel of three judges initially sentenced the three generals to life imprisonment, but reduced the sentence since the plot was unsuccessful, according Turkish state media. The three were accused of being the masterminds of the coup.
Dogan, one of the generals, said in his defense, "Here we see a process unfolding to make the soldiers of Mustafa Kemal (Ataturk, the founder of modern Turkey), who give their lives for their country, to pay the price of their commitment to the Republic and its principles," according to Al Jazeera.
The AP had slightly different figures for the convictions, reporting that 326 were convicted, including the three generals. It said 36 were acquitted of involvement in the conspiracy, while three other defendants had their cases postponed.
The 2003 plot involved bombing historic mosques in Istanbul in order to ignite conflict with Greece, thereby facilitating a military coup, Al Jazeera said.
The plot, referred to as Balyoz, or "Sledgehammer" in English, was seen as a reinforcement of the shift away from military power to civilian authority in Turkey, according to CNN.
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The defendants said the plot was simply a military exercise held by the army.
"The decision seems to be designed to set a precedent and give a strong signal to the armed forces that the days of meddling in politics are over," Suat Kiniklioglu, a senior member of Turkey's ruling Justice and Development Party, told CNN in an email. "Anyone attempting to discredit or overthrow a democratically-elected government in the future will think twice."
The Wall Street Journal noted, "Most people in Turkey see the verdict as the latest blow to the military, which once was the country's leading political player and self-appointed defender of the secular republic, established in 1923 by Mustafa Kemal Atatürk, who was also its first president."
The AP noted that Turkey's generals had staged three coups since the 1960s, forcing an Islamist government to quit in 1997.
All the officers are expected to appeal the verdicts.
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Here is a report from Al Jazeera: