Disunion follows the Civil War as it unfolded.

José Quintero’s reputation was soaring upon his return to Richmond in mid-August 1861. He had travelled the width of the Confederacy to deliver the rarest of gifts for the Southern capital: much better than a fine box of cigars, the Cuban-born Southern special agent brought good news from Mexico.

Despite a frenzy of activity, Confederate diplomacy was not bearing its anticipated fruits in the nation’s first summer. King Cotton had failed to induce recognition from Britain or France, and Richmond had heard nothing from Mexico City, where ambassador John Pickett’s boorish antics and intercepted dispatches, laden with contempt and condescension for his hosts, confirmed the Juarez government’s worst suspicions of the Southern cause — namely, that it had less interest in diplomacy, per se, than it did in southward expansion.

Yet 600 miles to the north of the Mexican capital, Quintero achieved one of the Confederacy’s most stunning diplomatic successes. In his negotiations with Santiago Vidaurri, governor of the Mexican border states of Nuevo Leon and Coahuila, the southern agent discovered a capable ally who offered more than his “great friendship”: Vidaurri promised border security, the supply of vital war material and an outlet for Southern cotton; most astonishingly, he proposed the outright annexation of his territories.

Adhering to the instructions from Richmond, Quintero had arrived in Vidaurri’s capital, Monterrey, with modest aims. He explained to Vidaurri during their meeting on June 23 that his chief concern was simply to establish cordial relations with Nuevo Leon and open discussions about security along the frontier.

The Dolph Briscoe Center for American History, the University of Texas

Vidaurri made it clear he did not have the authority to conduct foreign diplomacy — and then, in the same breath, offered to negotiate on behalf of his national government. Vidaurri stressed that border security was a high priority of his own, as he was actively in pursuit of Juan Cortina, the marauder who had sacked the border town of Brownsville, Tex., in 1859 and who was rumored to be gathering a force for additional raids across the Rio Grande. Furthermore, Vidaurri assured Quintero he would not allow Union troop movements through his territory and would do everything in his power to gather similar assurances from his fellow border-state governors.

The trading houses of Monterrey, Vidaurri told his guest, could provide the South with essential war supplies — not only lead, powder, saltpeter, copper and bronze, but also flour, cloth and shoes. Everything could be had in exchange for cash or cotton, and Vidaurri vowed to exercise his “moral influence” in Tamaulipas, the state bordering Texas and the Gulf of Mexico, to keep its port of Bagdad open to the Confederacy.

Vidaurri then divulged his greatest ambition to Quintero, something his enemies and allies alike had long suspected: that the governor was “anxious to establish the Republic of the Sierra Madre.” With the coming of the Civil War, Vidaurri suggested the time was ripe for his region to break with the central government in Mexico City and join the nascent Confederacy. Vidaurri stressed the similarities between his region and the Southern states: Mexico’s northern frontier was more geographically and commercially aligned with Texas than distant Mexico City, and annexation would further the process of Americanization that was already in progress.

Vidaurri’s states’ rights philosophy was well-suited for the Confederacy. The caudillo in Mexico City had ruled Nuevo Leon and Coahuila since 1855 under the Plan of Monterrey, a constitution that asserted state sovereignty and maintained a militia independent from federal control. Vidaurri exercised this autonomy, time and again putting his regional interests before the concerns of national politics; on several occasions he withdrew his troops from the liberal forces in the War of the Reform in order to consolidate his position in the north.

But there were also difficult incongruities between Vidaurri’s states and the Confederacy: Nuevo Leon’s constitution explicitly outlawed slavery, and the region had a proud history as a haven for runaway slaves, who with a year of gainful employment could even earn the right the vote. The backbone of his state revenues, moreover, depended on the customs receipts he would stand to lose once incorporated into the Confederate nation.

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So why was Vidaurri so eager to align with the nascent Confederacy? Political survival. He had lost his best general and military strategist, Juan Zuazua, to assassination that winter. With the end of the Reform wars, President Benito Juarez was consolidating federal control and was sure to challenge Vidaurri’s virtual independence along the northern frontier. And if Juarez did not unseat the northern caudillo, a European power might — France and others were already making noise about invading Mexico over its debts.

Though highly impressed with Quintero’s mission, Jefferson Davis wisely refused Vidaurri’s offer of annexation. Southern Democrats, including Davis, had been advocates of expansion into Mexico throughout the 1850’s, but a primary motive for acquisition, maintaining the balance of power in Congress between slave states and free soil, no longer existed. Moreover, for an independent South, Manifest Destiny came with serious drawbacks. A formal union with Vidaurri’s realm would put northern Mexico’s ports within jurisdiction of the Union blockade, chocking a vital outlet for Southern exports. Additionally, annexation would draw the rest of Mexico into war against the South.

Potentially even more damaging, such a union would likely scuttle one of the Confederacy’s best hopes for European recognition. Davis believed Napoleon III’s anticipated intervention into Mexico would spark a war between the Union and France, opening the possibility of a Franco-Confederate alliance. Southern annexation might dampen this potential conflict, while surely antagonizing a potential ally.

Davis’s rejection of Vidaurri’s offer didn’t mean the end for Quintero, though. In reward for his efforts, he was assigned to a permanent post in Monterrey. But there his diplomatic reputation was immediately put to the test. On his way back to Nuevo Leon, he learned that Jose-Maria Carvajal, a Virginia-educated filibuster, was organizing a force outside Brownsville to invade northern Mexico. Quintero, worried about the implications for cross-border diplomatic relations, alerted the local commander, John Ford, and Texas Governor Francis Lubbock.

But to his dismay, neither acted; Ford was an old compatriot of Carvajal’s, while Lubbock had other concerns at hand. In March 1862 Carvajal attacked Matamoros, just across the border. Vidaurri was outraged, and told Quintero as much. Quintero immediately offered his resignation in a blistering report to Richmond:

The General Government of Mexico as you are well aware sympathizes with the Black Republicans. We have, however, succeeded in securing the friendship of the Governors of the frontier states and are now on the eve of incurring the their enmity, on account of the band of robbers who are permitted to abuse the Hospitality of Texas … I earnestly request the Department to appoint a person to succeed me who may have more influence … with the military at Brownsville.

In response to the raid, Vidaurri closed border and later added a 2 cent per pound levy on all cotton that crossed the Rio Grande. Quintero, who rescinded his resignation, soon managed to negotiate a reduction in the tariff, and his appeal to Richmond eventually led to Carvajal’s arrest. Tempers subsided; though similar border incursions would threaten commerce for the duration of the war, both sides had too much to gain for commerce not to continue.

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Indeed, Quintero proved an integral tie between the two countries, and Vidaurri remained a staunch ally of the South. The governor refused a June 1862 request by the United States consul, C. B. H. Blood, for an official letter respecting Union commercial goods in his state. Later that same month, when President Juarez ordered the governor to “cease all intercourse with the Confederate States, under whatever circumstances,” Vidaurri refused, saying that he could not risk crippling the commerce in his region.

The alliance proved vital to the South: northern Mexico became a major outlet for its cotton, accounting for approximately 20 percent of wartime exports. Though the long wagon hauls through the rugged south Texas corridor ate up much of the value of the crop, the route proved competitive with the dangers of blockade running, as testified by the 125 ships at a time anchored off the coast near Matamoros.

But all good things come to an end. By 1864, the French invasion had pushed the Juarez government into northern Mexico, and Vidaurri was forced to choose between the central government and a foreign power. The master of self-preservation sought the winning side — and chose to back the French. When the French fell to Porfirio Díaz in 1867, he was arrested and executed.

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Sources: Ronnie Tyler, “Santiago Vidaurri and the Southern Confederacy”; Frank Owsley, “King Cotton Diplomacy”; Thomas Schoonover, “Dollars Over Dominion”; David George Surdam, “Northern Naval Superiority and the Economics of the American Civil War.”

William Moss Wilson is a writer based in Santiago, Chile.