This is the 150th anniversary of one of the Civil War’s most destructive and controversial campaigns. After Confederate armies had used the Shenandoah Valley to launch several invasions of the North, Union Gen. Philip Sheridan unleashed a hundred-mile swath of flames that left vast numbers of civilians tottering toward starvation. Unfortunately, the burning of the Shenandoah Valley has been largely forgotten, foreshadowing how subsequent brutal military operations would also vanish down the memory hole.

In August 1864, supreme Union commander Ulysses S. Grant ordered Sheridan to “do all the damage to railroads and crops you can. If the war is to last another year, we want the Shenandoah Valley to remain a barren waste.” Sheridan set to the task with vehemence, declaring that “the people must be left nothing but their eyes to weep with over the war” and promised that, when he was finished, the valley “from Winchester to Staunton will have but little in it for man or beast.”

Some Union soldiers were aghast at their marching orders. A Pennsylvania cavalryman lamented at the end of the fiery spree: “We burnt some sixty houses and all most of the barns, hay, grain and corn in the shocks for fifty miles [south of] Strasburg … . It was a hard-looking sight to see the women and children turned out of doors at this season of the year.” An Ohio major wrote in his diary that the burning “does not seem real soldierly work. We ought to enlist a force of scoundrels for such work.” A newspaper correspondent embedded with Sheridan’s army reported: “Hundreds of nearly starving people are going North not half the inhabitants of the valley can subsist on it in its present condition.”

After one of Sheridan’s favorite aides was shot by Confederates, Sheridan ordered his troops to burn all houses within a five-mile radius. After many outlying houses had been torched, the small town at the center — Dayton — was spared after a federal officer disobeyed Sheridan’s order. The homes and barns of Mennonites — a peaceful sect who opposed slavery and secession — were especially hard-hit by that crackdown, according to a 1909 history of Mennonites in America.

By the end of Sheridan’s campaign, the former “breadbasket of the Confederacy” could no longer even feed the women and children remaining there. An English traveler in 1865 “found the Valley standing empty as a moor.” Historian Walter Fleming, in his classic 1919 study “The Sequel to Appomattox,” quoted one bedeviled local farmer: “From Harpers Ferry to New Market, which is about eighty miles, the country was almost a desert… . The barns were all burned; chimneys standing without houses, and houses standing without roof, or door, or window.” John Heatwole, author of “The Burning: Sheridan’s Devastation of the Shenandoah Valley” (1998), concluded: “The civilian population of the Valley was affected to a greater extent than was the populace of any other region during the war, including those in the path of Sherman’s infamous march to the sea in Georgia.” Unfortunately, given the chaos of the era at the end of the Civil War and in its immediate aftermath, there are no reliable statistics on the number of women, children and other civilians who perished thanks to “the burning.”

Some defenders of the Union tactics insist that there was no intent to harshly punish civilians. However, after three years of a bloody stalemate, the Lincoln administration had adapted a total-war mindset to scourge the South into submission. As Sheridan was finishing his fiery campaign, Gen. William Sherman wrote to Grant that “Until we can repopulate Georgia, it is useless to occupy it, but the utter destruction of its roads, houses and people will cripple their military resources.” Sherman had previously telegrammed Washington that “[t]here is a class of people — men, women and children, who must be killed or banished before you can hope for peace and order.” President Lincoln congratulated both Sheridan and Sherman for campaigns that sowed devastation far and wide.

After the Civil War, politicians and many historians consecrated the conflict as a moral crusade and its sometimes-grisly tactics were consigned to oblivion. The habit of sweeping abusive policies under the rug also permeated post-Civil War policy toward the Indians (Sheridan famously declared, “The only good Indian is a dead Indian.”) and the suppression of Filipino insurgents after the Spanish-American War. Later, historians sometimes ignored U.S. military tactics in World War II and Vietnam that resulted in heavy civilian casualties.

The failure to recognize how wars routinely spawn pervasive brutality and collateral deaths lowers Americans’ resistance to new conflicts that promise to make the world safe for democracy, or rid the world of evil, or achieve other lofty sounding goals. For instance, the Obama administration sold its bombing of Libya as a self-evident triumph of good over a vile despot. Instead, chaos reigns in Tripoli. As the administration ramps up bombing in Syria and Iraq, both its rhetoric and its tactics echo prior U.S. misfires.

Since 1864, no prudent American should have expected this nation’s wars to have happy or uplifting endings. Unfortunately, as long as the spotlight is kept off atrocities, most citizens will continue to underestimate the odds that wars will spawn debacles and injustices that return to haunt us.

James Bovard is the author of “Attention Deficit Democracy” (Palgrave, 2006) and “Lost Rights” (St. Martin’s, 1994).