Something called the "deep state". It's a little complicated, but apparently there is an organization (or more than one) connected with current and former officers in the Turkish military that is anti-republican and pro-Kemalist. Various terrorist actions over the past several decades have been ascribed to this "Ergenekon", and several hundred people have been arrested, but the problem is it's awfully hard to tell where the treason ends and the purges-to-clear-the-army-of-the-current-prime-minister's-political-opponents begin.