Known as 'Testa di ferro' or 'Ironhead' because of his military prowess, Emmanuel Philibert, Duke of Savoy was a skilled political strategist and one-time suitor to Lady Elizabeth Tudor, later Queen Elizabeth I. He was the second cousin and nephew by marriage of Holy Roman Emperor Charles V and first cousin of his successor, Philip II of Spain. He served Charles V in the war against Francis I of France and distinguished himself by capturing Hesdin in July 1553. In the same year he succeeded his father as Duke of Savoy; however, the honour was a titular one as most of the hereditary lands had been occupied and administered by the French since 1536. Emmanuel Philibert continued to serve the Habsburgs in hopes of recovering his lands and was Governor the Netherlands under Philip II from 1555 to 1559. As leader of the Spanish invasion of northern France; the Duke won a famous victory at Saint-Quentin in 1557. With the signing in 1559 of the Peace of Cateau Cambrésis between France and Spain, the duchy was restored to Emmanuel Philibert and he married the French King Henri II's sister, Margaret of France, Duchess of Berry. Emmanuel Philibert spent the remainder of his life regaining lost territories, shrewdly taking advantage of European squabbles to reclaim land from both France and Spain.

It is possible that this portrait of the duke was painted during a visit to England in 1555, when Mor was known to have been in the country also. Alternatively it may have been executed to commemorate the victory of the Spanish over the French at the Battle of St Quentin in 1557. The painting was acquired by Charles I as the 'fellow peece' to Mor's 1554 signed portrait of Christina of Denmark (RCIN 405799), which was incorrectly identified during in the seventeenth century as the Duchess of Savoy. Given that there was no living Duchess of Savoy in 1554 and Emmanuel Philibert did not marry until 1559, it is unlikely that the two works were created as a pair. However, Christina of Denmark is known to have been in England at the same time as Emmanuel Philibert and it was rumoured that the two had signed a marriage contact. Though the marriage never took place, this may explain how the portraits came to be erroneously paired.

Born in Utrecht, Anthonis Mor van Dashorst was active in the southern Netherlands, Italy, Spain, Portugal and England during the course of his career. As court painter to Philip II of Spain, he painted members of the most powerful ruling élite in 16th century Europe. His style of portraiture was in the Netherlandish tradition of his master, Jan van Scorel but was also influenced by the work of Titian. He is credited with establishing a distinctive new style of portraiture that combined austerity and a formality of pose with penetrating insights into his sitters' characters. Typically Mor painted his sitters in three-quarter-length, with a three-quarter-view and strong lighting from one side.

This bold portrait shows the duke aged about twenty five. Painted life-size in three-quarter, he wears an ornate suit of armour and the collar of the Golden Fleece, of which he was made a knight in 1546. A strikingly similar suit of armour surviving in the Waffensammlung at Vienna has been proved to have belonged to Emmanuel Philibert and is almost certainly that depicted in this portrait. The red sash worn over the left shoulder identifies the sitter as a commander of one of the Spanish armies. Although the condition of the painting makes attributing the painting difficult, the composition and pose of the sitter are consistent with known works by Mor of the 1550s. Additionally, the panel is of a standard sized favoured by Mor during this period.