America’s 12th president died in July 1850 from a sudden attack of gastroenteritis, brought on by consuming a copious amount of cherries and iced milk on a blisteringly fetid Washington day. Perhaps never in history has a cold snack been so ill-advised, or led to such awful results.

The sudden death of Zachary Taylor, just 16 months into his presidency, was a tragedy in more ways than one.

For at a time of increasingly bitter polarization, Taylor — a president but not a politician — had been exactly the esteemed and celebrated leader America needed. The popular former war hero was first and foremost an American nationalist, determined to rise above region and party. Indeed, when it came to politics he had resisted taking sides all his life. During 40 years in the military, he had never voted for president, because he never wanted to be in the position of having to serve under a commander-in-chief whom he had voted against.

Taylor was born in Virginia, and he owned Mississippi and Louisiana plantations along with 150 slaves. So his election in 1848 had reassured Southern hardliners, who assumed he would be with them on the issue they cared about most: expanding slavery to the West.

But Taylor, it turned out, was no Southern partisan. Notwithstanding his own unclean hands, he had no sympathy for the slavers’ demands, and only contempt for their threats of secession. As a candidate for president Taylor had spoken blandly of compromise, but once in office he made it clear that for him nothing was more important than preventing disunion. “For more than half a century … this Union has stood unshaken,” he told Congress in December 1849. “Its dissolution would be the greatest of calamities.” He would meet any threat of disunion, he warned, with every power of the presidency.

Taylor was still a child when his family moved to Kentucky, and he grew up, in historian Catherine Clinton’s words, “wearing a coonskin cap and leather moccasins, a son of the frontier.” He never had more than a rudimentary education, but through family connections — his second cousin was James Madison — he was commissioned a first lieutenant in the US Army.

Military life proved a good fit for his abilities. He spent most of his Army years on the frontier, and was first praised for his gallantry and coolness during the War of 1812. Taylor’s reputation and rank rose as he led troops in the Black Hawk War and the Seminole War, and from his soldiers he acquired the nickname “Old Rough and Ready.” But it was his role in the Mexican War that brought him national renown.

In the spring of 1846, Taylor was ordered to move an army of 4,000 to the disputed territory along the Rio Grande, where tensions were running high between the United States and Mexico. He quickly won a pair of victories at Palo Alto and Resaca de la Palma, then captured the Mexican stronghold of Monterrey. His supreme triumph was the battle of Buena Vista, where he led his men in a stunning victory over a Mexican force that outnumbered his by three to one.

The Mexican War added a vast swath of territory to the United States — all of California, plus most of Arizona, Nevada, Utah, Colorado, and New Mexico — and plunged the nation into a vehement debate over whether slavery should be allowed in the new lands. Taylor, lionized as the hero of the war, was soon being touted as presidential material. As Dwight Eisenhower would be a century later, Taylor was wooed by admirers in both leading parties. Among those promoting him for the White House were Abraham Lincoln, an Illinois Whig, and Jefferson Davis, a Mississippi Democrat.

Taylor eventually declared himself a Whig and became the party’s presidential nominee. But he was still no partisan loyalist. To the consternation of many Whigs, he told one interviewer that he was not a party man “and if elected cannot be president of a party, but the president of the whole people.” He said he would let Congress determine the nation’s policies. But Taylor had never been a passive general. He wouldn’t be a passive commander-in-chief.

It soon became clear that the new president was a Southerner with Northern principles. On the burning issue of the day, he weighed in forthrightly. Taylor assured antislavery activists that there would be no expansion of slavery, and issued a blunt warning to Southern lawmakers who threatened to secede: “If it becomes necessary I’ll take command of the army myself,” he told them. “If you are taken in rebellion against the Union I will hang you with less reluctance than I hanged deserters and spies in Mexico.”

Nor would he be led by the Whig grandees on Capitol Hill.

To resolve the intensifying struggle over slavery, Kentucky Senator Henry Clay, the Whig Party’s “Great Compromiser,” proposed an elaborate package intended to satisfy all sides. Clay’s omnibus, which was strongly supported by Daniel Webster of Massachusetts, included the admission of California as a free state, the establishment of Utah and New Mexico as territories with slavery left optional, an end to slave sales (but not slavery itself) in Washington, D.C., and a stringent new fugitive slave law.

Taylor blocked Clay’s compromise. He wanted California and New Mexico admitted as free states without preconditions — especially an odious law requiring Americans to return escaped slaves.

That was where matters stood on July 4, when the president devoured his tainted cherries and milk. He died five days later. Vice President Millard Fillmore — nativist, slavery-appeasing, and a thoroughgoing party man — became president. He readily signed the Compromise of 1850, thereby kicking the slavery can a little further down the road.

Had Taylor lived, might America have been spared its deadliest war? If anyone could have saved the Union without bloodshed, it was likely this president who was an American hero, not a politician. Taylor inspired in Americans, Lincoln said, a level of “confidence and devotion” that no other leader of the age could evoke. His untimely death was a calamity. America has had many presidents were more polished and educated than “Old Rough and Ready.” It has had very few who loved their country more fiercely.

(Jeff Jacoby is a columnist for The Boston Globe).