Noel Malcolm's new book Useful Enemies centers on learning from the Turks

In 1534 an Ottoman delegation was in Paris to discuss a plan to unite France and Turkey against their shared enemy, the Habsburg empire. That François I should lavish courtesies on infidel diplomats was bitterly resented by French Lutherans, who were being persecuted after the “affair of the placards”: a scandalous denunciation of the Catholic mass had been discovered pinned to the door of the royal bedchamber; the Turkish visitors were escorted past pyres that would be fed by Protestant heretics.

A decade later the Franco-Ottoman alliance was so fixed a part of the European scene that François allowed a Turkish fleet under Hayreddin Pasha to winter in Toulon, the Mediterranean port having been emptied of its Christian inhabitants. The church bells were silenced and cantatas in the cathedral gave way to the call to prayer.“Looking at Toulon,” remarked an eyewitness after the Ottoman sailors had settled in, “you would say that it was Istanbul, with great public order and justice.”

Much of Europe affected to be scandalised by the alliance of France’s “very Christian king” with Sultan Suleyman I, the “Magnificent”, whose aim was to make Muslim Turkey the continent’s superpower. But as Noel Malcolm explains in Useful Enemies, the alliance was only the most overt of the accommodations that Europeans made after the Ottomans first exploded into the Balkans in 1362.

It is often assumed that the Turks were shoehorned into Europe’s political system during the colonial expansions of the 19th century; in fact they made their disruptive entry into the “concert of powers” 500 years earlier. To the substantial European inventory that Suleyman inherited on his accession in 1520, he quickly added Rhodes, Belgrade and Buda; only a stout Austrian defence stopped him capturing Vienna in 1529.

Far from being divided neatly between the Christian and Muslim worlds, southern and central Europe seethed with opportunism and expediency. A Christian Slav boy kidnapped by corsairs ended up as Suleyman’s grand vizier before falling foul of the sultan’s wife, herself the daughter of an Orthodox priest; the son of the Venetian doge became Istanbul’s top plutocrat. Slavery supplied the sultan’s armies, galleys and chancellery, a global enterprise under which as many as 1 million Christian Europeans – some from as far north as the Irish Sea – were enslaved between 1530 and 1640.

Suleyman’s northward thrust was facilitated by the Reformation, religious authority leaching from the pope and any possibility of concerted European action foreclosed. The sultan gave guarded approval to Martin Luther’s efforts to end Catholic superstition; he referred to the German reformer as “a great man, but he has not yet arrived at the enlightenment we enjoy”. Luther’s attitude towards the Muslims hardened the closer they got to Germany. In 1518 the year after he fixed his famous Ninety-Five Theses to the church door in Wittenberg, he described the Ottomans as preferable to the more cruel, more insatiable “Turks” of the Catholic church. But in 1529, the year of the siege of Vienna, Luther identified the sultan as the devil incarnate; death in battle with him was a passage to heaven.