Most historians view the brothers as pirates and slave traders, yet Turkish schoolchildren are taught the brave exploits of Oruc Reis (Turkish for “chief”) and Barbarossa Hayrettin (“best of the faith”). Now, Mr Erdogan uses seismic research vessels named after them to signal his country’s desire to defend its maritime rights and challenge regional powers.

Devised by retired naval officer Cem Gürdeniz, it views the eastern Mediterranean, the Aegean and the Black Sea – to be Turkey’s Blue Homeland. It first made headlines a year ago when Mr Erdogan gave a speech in front of a map laying out Turkish control over more than 460,000 square kilometres in those three seas.

Two weeks ago, the Turkish presidency marked the anniversary of that 1538 victory over Christian powers with a video re-enactment of Hayrettin battling Crusaders. “The blood of my ancestors flows through my veins,” the President’s communications head, Fahrettin Altun, said in a tweet releasing the video. “We die and take lives for the blue homeland.”