A century and a half ago, the United States and Mexico were two young nations just learning how to administer the vast territories wrested from their former masters. The bloody but largely forgotten war they fought over much of that territory shaped the borders, populations, and political identities that each has carried into modern times.

From the war of borders that began in April 1846, the two countries emerged two years later with starkly different prospects. North Texas public television station KERA reexamines the story of this conflict through the eyes of both sides. Its four-hour documentary, The U.S.-Mexican War, offers perspectives on a war that has almost disappeared from our collective memory.

Debuting nationally on September 13 and 14, The U.S.- Mexican War builds a sweeping narrative around a simple dispute: the U.S. demanded its neighbor's land, and Mexico refused. Both sides were unrealistic -- the U.S. in expecting Mexico to part willingly with nearly half of its vast territory, and Mexico in expecting to hold back the marchers from the north. Though Mexico could not out-duel the more experienced U.S. military, the young nations matched each other in resolve, cutting an erratic and bloody path. The negotiating game between Mexican President Antonio Lopez de Santa Anna and U.S. President James Polk has occupied countless scholars, just as the battles at Buena Vista and Cerro Gordo loom as classic encounters to study.

The war's relevance echoes today. A ravaged Mexico would descend into political chaos -- suffering an invasion from France and a series of brutal military dictatorships -- that would not rekindle democracy until 1910, leaving the nation underdeveloped technologically and economically. The U.S. would make strides toward its status as a world power with the addition of a half-million square miles of new territory -- land that is now the states of California, Arizona, New Mexico, Utah, Nevada, and parts of three others -- and all the natural resources, valuable property, and scenic treasures they contain.

Those conflicting legacies make for complicated storytelling, an obstacle KERA strived to overcome by embracing historians and resources from both countries.

"The bi-national nature of the project was our biggest challenge -- it always, in a way, had two heads," says Rob Tranchin, the program's co-producer and writer. "We were trying to account for both the U.S. and Mexican perspectives without having each cancel out the other point of view."

Tranchin says The U.S.-Mexican War was born in the mind of KERA producer Sylvia Komatsu in 1991 after seeing an exhibition of daguerreotypes with images from the battlefields. She soon won the aid of experts and historians steeped in U.S.-Mexican history.

The shadowy territorial dispute offered the film's producers a wealth of poignant storytelling opportunities. The Mexican nation was struggling to manage the huge territory it won from Spain in 1822 after its war for independence, lurching from one strong-handed ruler to the next in the search for political stability and unity. A robust United States was eager to expand to the shores of the Pacific on the call of "Manifest Destiny," but torn by the bitter confrontation over slavery -- and the pressure any new territory placed on the balance between slave and free states.

"I never really had thought of the United States as a young country," says Tranchin. "It was exciting to imagine our leaders arguing in terms of ‘what kind of country we want to be.'" Tranchin notes that the U.S.-Mexican War helped ignite the passions of the Civil War -- though the war with Mexico has long been eclipsed in our popular memory by the Civil War, which followed only a dozen years later.

The war was the first war in which the U.S. raised and trained a large army, transported troops by rail and sea, and made a major amphibious landing. It inspired Henry David Thoreau's famous treatise against the war, "On Civil Disobedience." It was the first big story for the U.S. penny press and the first major subject for the mass- produced color lithographs that dominated popular art. And it led to the switch from Mexican to U.S. citizenship -- overnight -- for tens of thousands of residents of the disputed territories.

The war and the debate over its progress became the stage for some of the era's main characters: Mexican president Jose Joaquin de Herrera, war hero and future U.S. president Zachary Taylor, Civil War general and U.S. president Ulysses S. Grant, poets Guillermo Prieto, and Walt Whitman.

The documentary weaves the ideas, events, and characters into a chronological narrative. Tranchin says the task was made more difficult because scholars differ on fundamental questions about the war.

"Did Polk have a vision of how the war was going to take place when he sent Taylor to the Rio Grande?" Tranchin asks rhetorically. "In the main, our American scholars felt that he didn't know -- that he was reacting as much as acting. In the main, our Mexican scholars felt Polk had a plan and was carrying out that plan. These are tricky shoals to navigate. When the narrator is involved, we make sure that the narrator doesn't plant a seed where we can't be sure."

The producers strived to use equal amounts of documentation. "We were trying to balance the wealth of information from the U.S. side with a relative lack of information on the Mexican side," says Tranchin. The task was eased by Apuntes, a document crafted in 1848 by fifteen writers, intellectuals, soldiers, and politicians in Mexico. "That account was a godsend. It was written in the moment, at a time when the passion was still high and the pain of the loss was still current."

The KERA team faced other critical decisions, such as whether to use voiceover translations of Spanish-speaking scholars and experts rather than subtitles. In the end the team followed the advice of a bilingual preview audience in Dallas, which said the program flowed better when presented in one language. Under a partnership agreement, a Mexican television station will prepare a Spanish-language version.

The biggest challenge lay in the storytelling itself, says Tranchin, particularly in describing the origins of the war. He cited the Texas War for Independence in 1836. "Most people imagine the war as the Alamo, which was a decade earlier," he says. "You've got to get viewers up to speed very quickly."

The producers also decided to set aside a technique they had explored -- threading in visual and textual links to the present-day U.S. and Mexico -- in favor of a narrative that focuses more closely on the period of the war and the pulse of its society. That decision allowed them to incorporate a greater number of artifacts, portraits, and images of the period, which join impressionistic battle recreation scenes, interviews with scholars, and voiceovers of writers of the time, including a caustically patriotic Walt Whitman and Kentucky farmer Jefferson Peak writing to his children from the front to remind them about their chores.

The series provides vignettes about characters, events, and individual battles, as well as historical theory. In describing the war's origins, scholar Jesús Velasco Márquez from the Instituto Tecnológico Autonómo de Mexico describes how the U.S. was "born modern," with a thirst for expansion and growth, while Mexico labored under the "almost medieval traditions" of its Spanish colonial roots. The turning point came, he says, when the new Mexican republic decided in 1823 to open Texas to settlers, offering cheap land and deferred taxes as a way to populate a barren area -- an offer that proved all too attractive.

"When Mexico tried to close the border, the immigrants came anyway -- illegally," the series explains. "Mexican residents in Texas soon found themselves outnumbered ten to one."

The story highlights another pivotal moment in 1835 when the Mexican republic decided to strip its colonists in Texas of their local authority and consolidate power in Mexico City. Championed by Santa Anna, the nation's young president, this decision stoked the passions of the determined followers of Sam Houston, fueling the drive for Texan independence and driving in the wedge that would eventually separate all of Mexico's northern lands.

"We made a present of Texas to the Americans of the north," Gen. Jose Maria Tornel y Mendivil wrote at the time, reflecting Mexican resentment and fear over the increasing U.S. influence in the region. "After we took them to our bosom, they destroyed us."

The program creates lively portraits of major personalities such as Santa Anna and Polk by relying on their own writings, on the observations of scholars, and on the opinions of contemporaries in news accounts, essays, and correspondence. Santa Anna emerges as an unstoppable force. He keeps Mexico in the war largely through a volatile mix of inspiration, military ignorance, unwavering resolve and tragic bravado -- which leads him to overrule sound advice from his own officers and ultimately lose major battles.

The story recounts both Santa Anna's disgraces -- his capture at San Jacinto while trying to disguise himself in a private’s uniform, and the loss of his artificial leg as he fled the battle at Cerro Gordo -- as well as his exceptional political skills, which allowed him to win the Mexican presidency on several occasions and to quell a rebellion even as U.S. General Winfield Scott was marching on the capital. It also draws the fateful connection between Santa Anna and Polk, who let the Mexican leader return from exile in Cuba during the middle of the war after Santa Anna had promised he would entertain negotiations.

"When you face Santa Anna with Polk, you're facing one opportunist with another," says historian David Pletcher, professor emeritus at the University of Indiana. Negotiations were Polk's preferred methods of achieving his objective: the addition of Texas, the Southwest, California, and Oregon to the Union. "To enlarge its limits is to extend the dominions of peace over additional territories and increasing millions," Polk said in his 1845 inaugural address about extending the U.S. frontier.

Polk set the war in motion when he embraced the annexation of Texas in 1845 -- a move that deeply angered Mexico, which had never recognized the Texan nation. Some scholars maintain that Polk's sending troops to the Rio Grande was an attempt to intimidate the Mexican government into selling its northern territories; others say it was a deliberate provocation to take the lands by force.

The series also captures Polk parrying with political opponents, who would label the conflict "Mr. Polk's War," and the uneasy relationships he had with top generals and diplomatic envoys.

Some of the richest detail, however, comes in painting the scenes of combat. The Battle of Buena Vista is told in the words of participants. New England private Sam Chamberlain describes how in February 1847, weary from a standoff with Mexican guerrillas, Zachary Taylor's troops encountered a surprise advance from a force three times larger, led by Santa Anna.

Chamberlain and others describe Taylor's sage choice of terrain to defend and the tactical leadership of Colonel Jefferson Davis of Mississippi. Despite losing six hundred and fifty of his five thousand men, Taylor prevailed that day. Rather than stay to fight the next day, Santa Anna withdrew his battered troops and retreated to Mexico City.

The series culminates with the negotiations that led to the Treaty of Guadalupe Hidalgo, in which Mexico ceded its lands. It makes clear that the document that ended the hostilities did not fully cover the scars, and that a battle of wills fought a century and a half ago still casts its shadow over the relationship of the two nations today.

Tom Stabile is a writer in New York City.

KERA received $672,000 in planning and production grants from NEH to make The U.S.-Mexican War.