The naked soldier holds the baby high above his head, about to smash the child on the bloody plinth at his feet. Around him, mothers shield their infants with their own bodies in a vain attempt to keep them from the fate of little blue bodies scattered all over the street.

The Massacre of the Innocents, by the Flemish master Rubens, churns with violence. It depicts King Herod's order for the slaughter of Jewish baby boys in the hunt for the newborn Jesus Christ.

Unknown for centuries, the masterpiece was even attributed to another artist, Frans de Neve. It fetched £49.5m at auction in 2002 after its rediscovery in a private house in Austria.

Now, as the highlight of the National Gallery's new Rubens show, it is on view in London for the last time before it returns to a private collection in Canada.

Innocence to condemn violence

Rubens's painting shocks. But it does so even more once you understand how he put it all together.

The Roman soldier has the same pose as the risen Christ bursting from the grave in a work by Michelangelo. And one of the hunkering women copies an ancient Greek sculpture of the goddess Venus taking a bath. Rubens condemned violence by using such innocent images to portray it.

The Flemish artist saw the results of violence firsthand. The start of the 17th century, when he worked in Antwerp, was a time of bloodshed in the Netherlands between the Protestant north and the Catholic south. Although Rubens became the leading artist on the Catholic side, he also played an important diplomatic role to help keep the peace after a truce in 1609.

A 'great thief'

Yet Massacre was not the only painting in which Rubens borrowed from others, the National Gallery exhibition reveals. He did so in almost every work.

"He was a thief, like any great artist," said the gallery's senior curator David Jaffe.

At 22 the young apprentice painter went on an eight-year study trip to Italy, where he was inspired by Michelangelo, Raphael and Caravaggio.

Rubens made an intense study of the human body. Over and over he drew ancient statues like the Laocoon group - a sculpture of the Trojan priest Laocoon and his two sons being silenced by sea serpents when they warned their people against the Trojan horse.

The Dutch artist also drew Willem van Tetrode's statuettes of muscular human bodies without skin from all angles.

The result was a burst of creative genius after his return to his home city of Antwerp in 1608.

Rubens had the remarkable ability to adapt the same material in different works. Roman Charity tells the story of a devoted daughter who offers her own breasts to feed her starving father in jail.

But the same figures become sexually charged in Samson and Delila: the naked-breasted temptress watches as the sleeping Jewish hero gets a haircut in her lap, draining his strength.

Rare drawing almost thrown away

In Ecce Homo ("behold the man"), Rubens reworked a drawing of a centaur - a pagan horse-man - into the heroic torso of the tortured Christ.

It is the first time for the centaur to be reunited with Ecce Homo. The drawing, which dates back to 1606, was found by accident among discarded drawings in a bin at a museum in Cologne four years ago.

Rubens was a master of innovation, Jaffe said. He excelled at painting ranging from religious and mythological to portraits and landscapes. "Nothing made him feel it was too hard to get the result."

Saint George, one of his earliest masterpieces, features the legend of the saint who killed a dragon to rescued a princess. The artist used the wooden end of his brush to give definition to the mane of the saint's horse. He also brought the stallion's nose to life with tiny blue and red dots - nearly 300 years before the French Impressionists came up with the technique. Rubens liked the painting so much that he never sold it.

One of the highlights of the exhibition is Rubens' sweet portrait of his eldest daughter Clara at age five, who died when she was twelve. With her rosy cheeks and wayward hair, it was a "happy snap just for the family".

By his mid-30s, Rubens' works were coveted by royal courts across Europe. As his fame grew, he employed an army of studio assistants who helped paint many of his later works.

But the first 15 years of his career, traced in this exhibition of 45 paintings and 30 drawings, shows his "early glory" undiluted by other hands, Jaffe said. It reveals how an apprentice painter became an "international superstar".

  • Rubens: A Master in the Making runs at the National Gallery from 26 October 2005 to 15 January 2006. Tickets on 0870 906 3891 or at