The main portrait shown here is of the Ottoman ruler Mehmed II Fatih (Muhammad II “The Conqueror” r.1451-81). It was painted, probably by Shiblizade Ahmed, on paper, about 1480. It shows the sultan sitting cross-legged, smelling a rose and holding a handkerchief.

There are many possible symbolic meanings for the rose: it might refer to the Prophet Muhammad, whose complexion is compared to rose petals, or to the Islamic peoples, protected by their armies (the leaves and thorns), or to the soft, cultured aspects of the sultan himself, as shown here.

Gardens, with their green hedges, flowers and fountains, were designed as cool and fragrant oasis-like paradises in the Middle East, especially when contrasted with the scorching desert and a life of action in the saddle.

In this painting, Mehmed wears a turban, composed of a cloth wound around a tall, velvet or silk turban finial. The stylised folds of his garments convey the sense of their voluminous richness while his contemplative, even melancholic expression gives the impression of a scholar-ruler. He no longer looks like a young man, but the ring on his thumb is an archer’s ring, so we know he is still an active hunter. Indeed, he was a very famous man of action in his youth, as his title, “The Conqueror”, reveals. In 1453, he conquered the great but depleted Byzantine capital of Constantinople which, situated on the Bosphorus, was a gateway between the Black Sea and the Mediterranean, between Asia and Europe. One of his satin and iron-chain battle shirts still survives - a brilliant yellow to dazzle and provoke the enemy and fix him in the eye of his soldiers.

His cultured side, demonstrated in this painting, is confirmed by his youthful sketchbook, which contains examples of his signature (tugra) and also sketches, some possibly by a palace tutor familiar with more Western styles of drawing. When he became sultan, Mehmed revealed his own interest in Western art, by asking the Venetian doge in Italy to provide him with “a good painter”.

The artist Gentile Bellini (1429-1507) stayed in the great Ottoman court for two years, painting the portrait of his host that is also reproduced here. The Italian artist aimed to show his subject in an illusionist space with realistic perspective and a consistent light source casting shadows.

Viewers could then imagine that they were looking through a window at a real person and, feeling themselves to be in a particular moment, could identify with the subject matter. (If the artist has idealised his subject, we are perhaps also less likely to notice and more likely to accept the portrait as accurate.) Shiblizade Ahmed’s painting was probably influenced by this Italian portrait, since he chose to show the bony structure of the sultan’s face, instead of conforming to the traditional Turkic and Chinese norms of beauty which was, for both men and women, a “moon face, almond eyes and a rosebud mouth”.

Islamic artists traditionally wanted an artwork to stand outside the present moment and behave more like a record or a symbolic representation.

Idealisation was part of their aim. A miniature painting of a court scene, for example, would show everything all at once, without regard for a realistic perspective. The blossom on the trees in the garden, the palace floor tiles (standing upright so as to be better seen), patterns and colours of textiles (all vertical with no perspective), a fountain, people coming and going and the ruler surrounded by his court - all would be shown to the best advantage in glorious colour. A sense of delight would be expressed (as in a Matisse painting) in the surface decoration of textiles, pottery and architecture, contributing to an impression of beauty and harmony.

These decorations, on tiles, metal and woodwork and carpets were created with pattern, a very important ingredient of Islamic art. Beautiful green and blue tiles, for example, surrounded worshippers in a mosque, creating rhythmic patterns that, in their repetition, combined complexity with order, leading to a sense of all-over harmony and geometry, boundless like the desert, but with the refreshing colours and patterns of plants in an oasis. The visual complexity of the delicate patterns and rich colours of walls and carpets must have been such a relief after the visual blankness of steppe or desert.

Even cruel battles were depicted with gorgeous colour and movement, extolling the exploits of the rulers and leaving out the excruciating reality.

The exhibition, Turks: A Journey of a Thousand Years, 600-1600, at the Royal Academy of Arts in London, shows, among many fascinating and beautiful things the two paintings reproduced here, as well as Mehmed’s mail shirt and sketch book, turban finials, carpets, tiles, porcelain, wall paintings, architectural scrolls, kaftans, books, exquisite metalwork and magnificently decorated doors.

Perhaps Mehmed II could sense his history stretching back over centuries to nomadic forebears on the steppes of Central Asia, to Xinjiang in China, and to Turfan. From c744 to 840, the Turkic Uighurs, one of several Turkic tribal unions, held sway in Turfan. The city was on the north-east section of the Silk Road - that great and most evocative ancient trade route linking China to the Mediterranean, which was travelled by the Venetian Marco Polo (1254-1324).

Look in the exhibition at a whole room of the wonderful, mysterious paintings of Muhammad Siyah Qalam (Muhammad of the Black Pen), if you want to sense the harsh life of these tough, nomadic peoples. Here you will catch a glimpse of their religious eclecticism - of shamanism and Chinese Buddhism - before they finally converted to Sunni Islam. You will see their skinny donkeys and flying demons, campfires, shamans and tigers.

The Uighurs were followed by the Seljuks, (c1040-1194) and after the mighty Mongolian conqueror Genghis Khan (c1162-1227) who, with his generals, subdued empires from the Black Sea to the Pacific. The equally terrifying Turkic conqueror Timur (1336-1405, also called Timur Lenk, meaning “Timur the lame” or, in English, Tamerlane or Tamburlaine) rose up to create his own empire, that of the Timurid Turks (c1370-1506).

When the Ottoman Turkic leader Mehmed II took Constantinople and renamed it Istanbul, from the Greek eis ten polin (“to the city”), he consolidated an empire that would last until after the First World War. This exhibition evokes the history of a people whose harsh life under tent or sky was warmed and made homely by richly patterned and coloured carpets and tents, and whose legendary speed and prowess outmanoeuvred more ponderous armies to create one of the largest and longest-lived empires in history.

Annie Harris is head of education at the Royal Academy Turks: A Journey of a Thousand Years, 600-1600, is at the Royal Academy until April. Tickets Pounds 11 adults, (concessions and school group tickets available) Tel: 0870 8488484 www.royalacademy.org.uk

www.turks.org.uk