Probably produced under the direction of Passchier Grenier, tapestry merchant, ‘The Conquest of Tangier,’ c. 1471-1475, wool and silk tapestry. (Paul M.R. Maeyaert/PAUL M.R. MAEYAERT/COLLEGIATA DE)

Neither time nor the Age of Mechanical Reproduction has been kind to the tapestries of Pastrana, a set of four large-scale, tremendously detailed propaganda pieces celebrating the exploits of 15th-century Portugal. Stored for centuries at a parish church in Pastrana, Spain, they were filled with dirt and prey to moths, light damage and corrosion from the original dyes used to color their threads.

Even now, after careful conservation, they fail to make much of an impact when seen in photographs or reproduced in books. The tumult of war depicted in their weave of wool and silk, the raised swords, bristling spears, flapping banners and blaring trumpets, all look flat, like the two-dimensional patterns on a jack, queen or king in a deck of playing cards.

But come face to face with them at the National Gallery of Art, where they are on display together for the first time in the United States, and they burst into life. These late Gothic works, made just before the Spanish “discovery” of the New World — and rare examples of 15th-century tapestry created in response to actual historical events — are fired with the energies of the Renaissance, the martial and intellectual restlessness that was already being felt up and down the coast of Africa and that would soon extend to North America.

The monumental panels, each measuring 12 by 36 feet, require a large room and ideal light to breathe. With space for the visitor to move around in front of them, taking in the detail and grand design, they become animate, and the density of visual data that makes them look confused on paper disappears. Pick a spot, work outward, follow the drama, and suddenly they resolve into a meaningful narrative.

“They are a little hard to figure out,” says Barbara von Barghahn, a professor of art history at George Washington University and a specialist on Portuguese and Spanish art. Barghahn, who will deliver a National Gallery lecture on the tapestries in December, suggests beginning with the banners of Afonso V, the Portuguese king who conquered the North African cities of Asilah and Tangier in 1471. Three of the tapestries document the battle at Asilah, and they feature Afonso prominently, arrayed in armor and fine cloth, riding on a richly caparisoned horse. The banners, which depict a water wheel shedding drops in all directions, become a leitmotif in the panels, identifying the king, his ships and his army.

The tapestries, probably made for display in a large public room of a royal palace, glorified Afonso, and his line, at a time when Portugal was in contest with Spain for regional dominance, eager to extend its commercial and military influence into Africa, and hungry for the accolades that the Catholic Church heaped on rulers who killed Muslims. The persistence of his banners as a visual element not only grounds the viewer, it reinforces royal hagiography.

The tapestries also feature long, horizontal blocks of text woven into the top of the panels, offering basic details of their narrative. According to one inscription, the landing at the town of Asilah was complicated by rough seas, which “made it extremely dangerous to disembark the soldiers on land.” In the center right of the panel, fragments of soldiers — a torso, a head, a helmet — are seen at odd angles to the otherwise strongly vertical and horizontal layout. These are some of the 200 men who drowned in the wreck of small and overloaded boats attempting the amphibious assault.

The king’s banners thread through the first three tapestries, beginning with a dense cluster of masts and rigging on the far left of the first panel, where they swirl with undaunted energy and expectation around the royal ships; continuing through the bombardment of the town in the second panel; and ending with another flourish on the right side of the last of the Asilah tapestries, where they accompany a crowded and chaotic scene of hand-to-hand combat during the final assault on the doomed town.

The conquest of Asilah cost its Muslim defenders some 2,000 dead and 5,000 captured, which helps explain why the last of the four panels, “The Conquest of Tangier,” feels very different, more orderly and restrained. Horrified by the fate of Asilah, and offered no hope of relief by local leaders, the people of Tangier abandoned their city to the Portuguese. The desolate Tangerines can be seen on the far side of the panel, making an orderly exit to the right, with babies slung over the backs of women and carefully tied bundles of possessions carried by the men. Over the ramparts of Tangier, a lone Portuguese soldier raises the victor’s flag. Otherwise, the city is empty and almost eerily calm.

The tapestries, now bug-free, newly cleaned, repaired and relined for greater strength, are historically invaluable. They document a moment when forces unleashed by burgeoning trade and cultural ambition were turning outward, from being the glory of Europe to the bane of the planet. In 1452, as Portugal struggled to establish a foothold in Muslim North Africa, Pope Nicholas V issued a papal bull allowing, even encouraging, Spain and Portugal “to invade, search out, capture, and subjugate the Saracens and pagans and any other unbelievers and enemies of Christ wherever they may be.” That included the right “to reduce their persons into perpetual slavery.” Thus began one of the ugliest chapters in human history — discovery and exploration would march hand in hand with conquest, murder and enslavement, all sanctioned by the church — with the consequences still unresolved.

They are also a rare extant example of tapestries made to celebrate specific historical events, as opposed to allegorical, legendary, biblical or ancient dramas.

“There are very few battle sets that survive from this period,” says von Barghahn, who compares them to a journalistic account. “It’s almost like a contemporary report,” she says. Tapestries, at the time more valuable than paintings, were a portable, practical art, carried from palace to palace, and sometimes even onto the field of war, where they decorated regal tents.

The tapestries were made only years after the events depicted, and one scholar in the exhibition’s accompanying catalogue calls them “unmatched in any form of the visual arts of the fifteenth century” for the detail and accuracy of their depictions of military paraphernalia. Portugal, von Barghahn points out, also lost an extraordinary artistic legacy when it was hit by the 1755 Lisbon earthquake, with its subsequent tsunami and devastating fires. “All of those objects that came back from the Orient, all the treasures of Africa — that was swept away,” she says.

The Pastrana Tapestries survived because they were in Spain, and though sequestered for centuries in the relatively inaccessible care of the church in Pastrana, they were deemed important enough to be whisked to safety during Spanish Civil War. One of the panels, “The Conquest of Tangier,” was seen at the National Gallery during the 1991-92 exhibition “Circa 1492: Art in the Age of Exploration.” But they make a stronger impact when seen together, and without the distraction of other treasures.

Scholars have noted one detail that will remain with any alert viewer of these enormous and variegated narratives. The faces of the enemy are rendered seemingly without comment, objectively and even sympathetically. Their headgear is different, and their swords and shields easily distinguish them from their Portuguese conquerors. But there is no demonization, just two armies opposing each other, each one filled with men wearing determined, serious and perhaps weary expressions.

That might be a source of some pride to people who take pride in Western civilization. But it also suggests a failure to see difference. Although the artist who designed the tapestries — there is debate about who that was — took great care over details of armor, dress and weaponry, at some point reflexive visual habits simply took over, and the North African cities of Asilah and Tangier were represented as typically Northern European cities. The delicate flowers and greenery that surround the Muslim citadels are the generic floral filler of the tapestry-makers of Tournai, in Flanders, where the panels were woven.

To see the other as one’s equal is admirable if they are, indeed, one’s equal. And the Portuguese who invaded North Africa in 1471 had good reason to see Muslims as formidable and sophisticated adversaries, after centuries of political, cultural and military engagement. But as Spanish and Portuguese adventurers turned their energies to other parts of Africa and to America, with often genocidal results, they would send back tales of contest with seemingly equal enemies, as if these new battles against technologically-less-advanced societies only continued the annals of chivalrous combat. But they weren’t equals, in any military sense. The failure to see that led to centuries of misery for conquered, enslaved and exploited peoples around the world.

The Invention of Glory: Afonso V and the Pastrana Tapestries

through Jan. 8 at the National Gallery of Art’s East Building. The gallery is open Monday through Saturday, 10 a.m. to 5 p.m., and Sunday 11 a.m. to 6 p.m. Admission is free.