In 1825, Sen. John Elliott of Georgia offered a picturesque image to justify America’s treatment of Native Americans: “Like a promontory of sand, exposed to the ceaseless encroachments of the ocean, they have been gradually wasting away before the current of white population.” Within the logic of his metaphor, expulsion of people and expropriation of property were not matters of human choice — they were natural, inevitable, even beautiful. What could be so bad about the lapping of tides against the shore? Critics of America’s policies toward Native Americans were naively resisting the ocean.

From the standpoint of Choctaw leader George Harkins, the situation demanded a different metaphor. A few years after Elliott’s maritime image, he likened his people’s position to a man surrounded on three sides by raging fire, and his only route of escape on the fourth side was water and a distant shore. “Who would say that his plunging into the water was his own voluntary act?” he asked.

The clash between these views forms the heart of Claudio Saunt’s extraordinary new history, “Unworthy Republic: The Dispossession of Native Americans and the Road to Indian Territory.” Saunt’s book is a major achievement, commendable for his candor about the horrors of expulsion and his illumination of the crucial role that Southern slaveholders — eyeing Indian lands to take over for themselves — played in shaping early 19th-century American Indian policy. This alone would make for an important study, but he also manages to do something truly rare: destroy the illusion that history’s course is inevitable and recover the reality of the multiple possibilities that confronted contemporaries. Things could have been otherwise. The “ocean” could have stopped itself.

On nearly every page, Saunt slices away the conventional euphemism of “removal” enshrined in the name of President Andrew Jackson’s 1830 Indian Removal Act, choosing instead the harsher and more accurate term “expulsion.” He calls American policy toward the indigenous tribes of the Southeast one of the “first state-sponsored mass expulsions in the modern world” and says that this expulsion was “the war the slaveholders won.”

In the first two decades of the 19th century, the American Indian land base diminished by almost 600,000 square miles, an area roughly the size of Alaska. Incredibly, this was only the beginning of a century of conquest and bloodshed. But as late as 1825, Cherokee and Creek peoples still occupied roughly a quarter of the present-day state of Georgia and numbered more than 10,000.

Many powerful politicians and landowners in Georgia wanted to change this. In 1821, Gov. John Clark expressed the ambition to replace “all the red for a white population.” A few years later, an editorial in the Savannah Republican signed by “A Native Georgian” praised the outspoken Georgia senator and governor George Troup for his determination to “maintain at all hazards, the inalienable rights you possess to your slaves and to your Indian territory!”

During debates before the passage of the Indian Removal Act, petitions opposing the legislation poured into Congress. Critics pointed out that Native Americans possessed a “perfect right” to their lands and cautioned against committing acts of “enormous injustice.” A group from Dartmouth College compared American policy to the “bloody conquests of Cortez and Pizarro.” Perhaps the strongest argument came from a young Cherokee scholar named David Brown, who asked Americans to consider a role reversal: “How would the Georgians receive a proposition from the Cherokees to exchange the land they now hold, (which originally belonged to the Cherokees) for a tract of country near the Rocky Mountains?”

There was one region from which no opposition emerged: Southern slave states. Rich plantation owners coveted the huge stretches of fertile land that indigenous peoples occupied, and some Southern politicians threatened to secede if Northerners interfered with their plans. Fears of federal intervention, of course, had another motive as well: the desire to avoid a precedent that might threaten their ownership of African slaves.

This belligerent states’ rights pose quickly evaporated once Southerners realized they would need federal support to implement the enormous undertaking of forcibly relocating thousands of people. The national government, however, outsourced many aspects of the expulsion, contracting with private companies that penny-pinched and cost-cut to maximize their profits. Not only was there inadequate food, shelter and medicine on marches across hundreds of miles of rough terrain, the government went so far as to bill deportees for the camping equipment of U.S. officers and the nails used to construct storehouses for supplies. Though difficult to calculate accurately, death rates from exposure, starvation, cholera and despair were shockingly high.

Saunt does not belabor current-day parallels, but they are impossible to miss. Jackson threatened not to back the reelection bids of congressmen tempted to vote their conscience; he stacked the Bureau of Indian Affairs and other agencies with incompetent patronage appointees; and he was still in office when, in 1836, Congress appropriated funds to construct a 1,200-mile wall of defense in the West to maintain “a continual surveillance” of the border.

What’s painful but essential to realize is how easily history could have been different. If only five congressmen had voted differently, if the president had chosen to enforce a crucial legal decision, or if more citizens in Florida, Georgia and Alabama had resisted plainly inhumane policies, one of the most shameful and cruel episodes in all of American history might have been avoided.

Unworthy Republic

The Dispossession of Native Americans and the Road to Indian Territory

By Claudio Saunt

396 pp. $26.95