BAD PRECEDENT.

By late 1814, it was clear that America was not winning the War of 1812. Washington, including the Capitol and the White House, was in ashes. New Englanders were so demoralized that they were considering secession. When British troops, hardened from battling Napoleon, set sail for Louisiana, some feared that America might not be able to hold on to its recent acquisition.

Into the national gloom, however, light broke. On January 8, 1815, a major general from Tennessee named Andrew Jackson stopped the British from taking New Orleans. The battle lasted less than two hours, but more than two thousand British soldiers were killed or wounded, compared with only a few dozen Americans. The victory had almost no practical effect. Although the news hadn't yet reached the Western Hemisphere, British and American representatives had negotiated peace, on Christmas Eve at the Treaty of Ghent, restoring the pre-war territorial boundaries. Nonetheless, Jackson's victory was a public-relations triumph. It "restored and inflamed the national self-love," as James Parton puts it in an elegant, pleasantly cynical 1860 biography. He achieved sudden and overwhelming popularity, which became, according to Parton, "the principal fact in the political history of the United States" for the next generation, a period that Arthur Schlesinger, Jr., famously called the Age of Jackson.

In the two months immediately following the Battle of New Orleans, however, Jackson put his glory in jeopardy, keeping a tight grip on civil liberties and seeming to take personally the restlessness of those under his control. He censored a newspaper, came close to executing two deserters, and jailed a state congressman, a judge, and a district attorney. He defied a writ of habeas corpus, the legal privilege recognized by the Constitution which allows someone being detained to insist that a judge look into his case. Jackson was fined for his actions, and, for the rest of his life, was shadowed by the charge that he had behaved tyrannically. In retirement, after two terms as President, he called on his reserves of political clout to get the fine refunded, and Congress ended up debating the legality of his actions in New Orleans for nearly two years. As Matthew Warshauer argues in a lucid and well-researched new book, "Andrew Jackson and the Politics of Martial Law" (University of Tennessee; $39.95), the debates changed the definition of martial law in American jurisprudence. They also set a precedent for granting emergency powers to the executive branch which remains a troubling legacy today.

A British visitor to America wrote that Jackson had "a game-cock look." He was a gaunt six feet one, with sallow skin, a lantern jaw, long, loose teeth, and iron-gray hair that stood straight up. A political enemy once likened him to an "exasperated rhinoceros." He relished violence almost to the point of connoisseurship. In fighting with a stick, he suggested aiming not for the head but the stomach; with a pistol, he advised aiming for the brain. Some thought that he stage-managed his ferocity for political effect. One anecdote has him chuckling in the Presidential office over an outburst ginned up to frighten away some petitioners: "Didn't I manage them well?" Whether this propensity sprang from nature or art, he knew how to put it to use. "What truly set him apart from other generals was his ability to motivate his men," H. W. Brands writes in an equable and fluent recent biography. For sticking by his troops when his superiors ordered him to abandon them Jackson was loved; his soldiers nicknamed him Old Hickory on account of his toughness. But for turning his cannons on soldiers who thought their term of enlistment shorter than he thought it was, and for having a teen-ager shot for refusing an order, he was feared. Like the God of the Old Testament, Jackson commanded both responses.

Shortly after reaching New Orleans, accordingly, Jackson threatened to kill collaborators. "Those who are not for us are against us," warned a broadside issued on his orders. The governor of Louisiana, William C. C. Claiborne, had described a "spirit of Disaffection" in the city, and there were indeed many opportunities for distrust. The British were thought to be encouraging the blacks to revolt, and the city's whites divided their loyalties between France, Spain, and the United States. Forty miles to the south, in the bay of Barataria, there were privateers, led by Jean Lafitte, a former blacksmith, and it was unclear which side they would take.

To reduce the uncertainties, Jackson recruited two battalions of free blacks. "Distrust them, and you make them your enemies," he explained to the governor; "place confidence in them, and you ...