Prosecutors said Ergenekon, named after a mythical place in central Asia believed to be the homeland of Turks, was made up of loosely connected branches with an eventual goal of toppling Erdogan’s government and restructuring Turkey on a nationalist footing.
The network was uncovered in June 2007 when weapons and explosives were discovered during an anti terrorist operation in an Istanbul suburb.
The trial is one of a series of cases in which members of the Turkish army, the second biggest in NATO, have faced prosecution for alleged coup plots against an elected government.
Deputy Prime Minister Bulent Arinc declined to comment on the verdicts on behalf of the government, but personally urged respect for the independent judiciary.