Throughout Ottoman history, however — despite the supreme "de jure" authority of the sultans and the occasional exercise of "de facto" authority by Grand Viziers — there were many instances in which local governors acted independently, and even in opposition to the ruler. On eleven occasions, the sultan was deposed because he was perceived by his enemies as a threat to the state. There were only two attempts in the whole of Ottoman history to unseat the ruling Osmanlı dynasty, both failures, which is suggestive of a political system which for an extended period was able to manage its revolutions without unnecessary instability.