In the American experience, anti-Semitic decrees have been virtually unthinkable. Religious liberty is enshrined in the Constitution, and early in his presidency George Washington went out of his way to assure the young nation’s Jews that “the Government of the United States … gives to bigotry no sanction, to persecution no assistance.” During the long centuries of Jewish exile, powerful officials had often promulgated sweeping edicts depriving Jews of their rights or driving them from their homes. In America, that could never happen.

But 150 years ago this month, it did.

In December 1862, with the Civil War raging, the Union Army’s efforts to control the movement of Southern cotton was bedeviled by illegal speculation and black marketeers. Like many of his contemporaries, Major General Ulysses S. Grant – then commanding a vast geographic swath called the Department of the Tennessee – shared a crude stereotype of all Jews as avaricious, corner-cutting swindlers. That ugly prejudice boiled over in General Orders No. 11, the most infamous anti-Semitic injunction in American history: “The Jews, as a class violating every regulation of trade established by the Treasury Department and also department orders, are hereby expelled from this department within 24 hours from the receipt of this order.”

The region commanded by Grant was home to several thousand Jews (including men in uniform serving under him). Fortunately, General Orders No. 11 had little direct impact on most of them. Jews were driven out of Paducah, Ky., and some towns in Mississippi and Tennessee, and there were accounts of Jewish travelers being imprisoned and roughed up. But a breakdown in military communications slowed the spread of Grant’s directive, and at least some officers had qualms about enforcing it. Brigadier General Jeremiah C. Sullivan, the Union commander of Jackson, Tenn., commented tartly that “he thought he was an officer of the Army and not of a church.”

What stopped the expulsion order cold, however, was the commander-in-chief. When word of Grant’s edict reached President Lincoln on January 3, 1863, he immediately countermanded it. “To condemn a class is, to say the least, to wrong the good with the bad,” the president declared. “I do not like to hear a class or nationality condemned on account of a few sinners.”

End of the story? In some ways it was just the beginning.

As historian Jonathan Sarna relates in a recent book, When General Grant Expelled the Jews, Grant’s order did his military career no harm. Within a few years he was commander of all Union armies and the Confederate surrender at Appomattox made him a national hero. He was elected president in 1868, and re-elected four years later.

Yet for the rest of his life, Grant was ashamed of having attempted to evict “Jews as a class” for offenses most of them had never committed. “What his wife, Julia, called ‘that obnoxious order’ continued to haunt Grant up to his death,” Sarna writes. “The sense that in expelling them he had failed to live up to his own high standards of behavior, and to the Constitution that he had sworn to uphold, gnawed at him. He apologized for the order publicly and repented of it privately.”

Not surprisingly, Grant’s order got a good deal of attention in the 1868 presidential campaign – the first time a “Jewish issue” played a role in presidential politics. Grant didn’t deny that General Orders No. 11 had grossly violated core American values. “I do not sustain that order,” he wrote humbly. “It would never have been issued if it had not been telegraphed the moment it was penned, and without reflection.”

But it was as president that the full extent of Grant’s regret became clear. He opposed a movement to make the United States an explicitly Christian state through a constitutional amendment designating Jesus as “Ruler among the nations.” He named more Jews to government office than any of his predecessors – including to positions, such as governor of the Washington Territory, previously considered too lofty for a Jewish nominee.

Grant became the first American president to openly speak out against the persecution of Jews abroad. In response to anti-Jewish pogroms in Romania, he took the unprecedented step of sending a Jewish consul-general to Bucharest to “work for the benefit of the people who are laboring under severe oppression.” All in all, the eight years of Grant’s presidency proved to be a “golden age” in US Jewish history. When he died in 1885, he was mourned in synagogues nationwide.

It was a remarkable saga of atonement. From scourge of the Jews to their great friend in Washington; from the general who trampled Jewish liberty to the president who made protection of their rights a priority. Only in America.

(Jeff Jacoby is a columnist for The Boston Globe. His website is www.JeffJacoby.com).