This great portrait of a Renaissance military man throbs with masculinity. Francesco Maria I della Rovere exudes potency from his beard and his darkly glittering armour to his sword pommel and baton. He also displays it by wearing a chain-mail codpiece. And yet, his melancholy face betrays a world weariness that undercuts all this phallic pomp.

King Henry VIII by Hans Holbein the Younger, available to view at the National Portrait Gallery from 12 September. Photograph: National Portrait Gallery

Henry VIII is a monster of a man in Holbein's lifesize design for a mural of the Tudor dynasty. His porcine tree stump of a head and vast chest are meant to terrify those approaching the king's presence, but all eyes are drawn to his magnificent codpiece, which unequivocally equates power and sexual prowess. The dagger at his side mirrors its symbolism and signifies his masculine readiness to harm those who cross him.

The 1540 Armour of Henry VIII. Photograph: Colin Davey/REX

Unless they are made of metal, clothes from the 16th century have rarely survived. This superb suit of armour preserved in the Royal Armouries (one of several of Henry VIII's sets that have stood the test of time) proves that Holbein did not tell lies: Henry really did wear a codpiece just as flamboyant as the one he flaunts in Holbein's portrait. It is just one of the ways in which his armour portrays Henry as larger than life.

Portrait of a Halberdier by Pontormo. Photograph: Corbis

The red codpiece of this young soldier peeps suggestively into the lower part of the painting to underline the symbolism of his erect staff weapon. It is a romantic painting of a virile youth. Pontormo's drawings of male nudes suggest he found men erotically fascinating. There is also a political idealism to this young soldier, as he stands ready to defend the Florentine Republic from its enemies.

Portrait of Antonio Navagero by Giovanni Battista Moroni. Photograph: Photoservice Electa/UIG/Rex

Almost everything about this portrait would have been acceptable in a Victorian portrait of a man of affairs. Navagero poses as if in the midst of business, letter in hand, leaning on his desk. He wears a fur-lined robe that reeks of status and wealth. His face is sensitive and intelligent. And yet no portrait in later ages of a Disraeli or Rothschild would flaunt the subject's manhood in this spectacular and biologically realistic red codpiece.

Young Knight by Vittore Carpaccio. Photograph: Mondadori Portfolio/Getty Images

This is a chivalrous codpiece, peeping out from the knight's armour like a red cock's crest. The medieval code of chivalry, still very much alive in 16th-century Europe, was ripe with such sexual imagery. Women gave knights items of clothing as favours. Jousts involved two men riding at one another with long lances in front of a largely female audience. This knight is dressed to impress with a heraldic totem between his legs.

Portrait of Ranuccio Farnese by Titian. Photograph: Alamy

No artist is as phallocentric as Titian. His men are men and his women lie waiting in the bedroom. In his unrivalled portraits, Titian displays a variety of codpieces with a variety of meanings. Here, he uses this bizarre (to modern eyes) item of clothing to signify that 12-year-old Ranuccio Farnese is already on the cusp of manhood.

This young man means business. He looks seriously out of the painting, a touch of menace in his eyes. Don't mess with this sombre character. Just to emphasise his authority and toughness, he flaunts his equipment in a prominent fiery codpiece. As in other Renaissance portraits, the use of red heightens none-too-subtle hints of sexuality and hot blood.

Alessandro Farnese by Alonso Sanchez Coello. Photograph: DEA/G Daglie Orti/De Agostini/Getty Images

This Renaissance military hero displays his manhood in the customary manner. It is striking that the men of Italy's most powerful aristocratic dynasties – compare Titian's portraits of a member of the della Rovere family and Ranuccio Farnese – are so often portrayed in codpieces. This item of dress is an image not just of personal potency but also the capacity of these influential clans to keep producing male heirs.

The Tempest by Giorgione. Photograph: Photoservice Electa/UIG/Rex

The bulging loins of the young man in this painting, along with his erect spear, make plain the nature of his interest in a young woman who sits semi-naked in the countryside. But she's a real person with real troubles. She is nursing her child, and has nowhere to feed it except here in the open. Is she homeless? Has poverty or disapproval driven her out of town? And why can the man see her only as a sex object when the reality of her desperate plight is so apparent? His codpiece makes him heartless in this troubling masterpiece.

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