Turkish retired Gen. Cetin Dogan, the former commander of the 1st Army, and retired Gen. Engin Alan were released from prison Friday along with 12 other suspects arrested as part of the Sledgehammer investigation, Hurriyet Daily News reported.

Gen. Dogan is accused of being the mastermind behind the alleged Sledgehammer conspiracy, which purportedly sought to stage a military coup against the ruling Justice and Development Party, or AKP. The decision to release him was made by the 9th Court for Serious Crimes, which evaluates objections and appeals on arrests.

The Sledgehammer plot, said to have been drafted in 2003, allegedly involves the military planning drastic measures to foment unrest in the country in order to remove the AKP from power. Those measures included bombing two major mosques in Istanbul, staging an assault on a military museum by people disguised as religious extremists and raising tensions with Greece by attacking a Turkish plane and blaming the incident on the Aegean neighbor.