Since an attempted coup against the president last summer, Mr Erdogan has set about arresting tens of thousands of suspected plotters and sympathisers, including soldiers, teachers, judges, politicians and journalists.
In April he won publical approval for constitutional overhaul which extends his powers and brings the country closer to autocratic rule. Despite all the tensions, however, Turkey remains an indispensable frontline ally for Nato.
A deal with the EU has seen Turkey help stem the tide of refugees to Greece and the country is keen as a vital partner in the fight against Isil.
Shortly after making Sunday’s heated speech at a mosque in Ankara, Mr Erdogan became unwell and had to be taken out on a stretcher.