Every major counterinsurgency waged by a Western power since the advent of mass-circulation media in the late 19th century has produced at least one scandal in which troops are accused of employing excessive force. The most famous occurred in 1968 when a U.S. Army company slaughtered several hundred inhabitants of the Vietnamese hamlet of My Lai.

But the current scandal, in which a Marine squad is accused of killing 24 Iraqi civilians in the town of Haditha, calls to mind two smaller-scale cases that made headlines a century ago: the trials of U.S. Marine Maj. L.W.T. "Tony" Waller and British army Lt. Harry "Breaker" Morant, the former arising from the Philippine war, the latter from the Boer War in South Africa.

Waller was court-martialed in 1902 for ordering the summary execution of 11 Filipino porters whom he suspected of treachery during a harrowing jungle hike in which 11 Marines died. The case became a sensation when Waller claimed that his commanding officer, Army Brig. Gen. Jake Smith, had ordered him to take no prisoners and to turn the island of Samar into "a howling wilderness." Waller was acquitted, but Smith was convicted of misconduct and forced into retirement.

The same year, Morant, an Australian poet and horseman, was tried for ordering the killing of a dozen unarmed Boers. Morant was found guilty and shot by a firing squad, along with another Australian officer. A third Australian received a life sentence but served fewer than three years.

These cases have certain similarities. First, the soldiers claimed to have been driven over the edge by enemy atrocities. Waller was operating in an area where, a few months earlier, a U.S. Army company had been butchered by insurrectos pretending to be friendly villagers. Morant was eager to avenge a close friend, Capt. Percy Hunt, who was captured, murdered and mutilated by the Boers. The Marines in Haditha apparently snapped after an insurgent bomb killed a beloved comrade, Lance Cpl. Miguel "T.J." Terrazas.

Second, for all the revulsion caused by their actions, a large part of society has been unduly eager to exonerate the accused. Both Waller and Morant claimed that they acted under orders and that they were (as the title of a book written by one of Morant's co-defendants had it) "Scapegoats of the Empire." Antiwar advocates have been eager to accept such explanations because they are convinced that the real culprits are not the rank and file but the architects of the conflict — a charge heard often during the Abu Ghraib affair and now over Haditha.

In talking to troops over the years, I've discovered that those most eager to hold military defendants accountable are not civilians but veterans of ground combat who have been in equally stressful situations and have reacted with greater restraint. They do not hold with actions that sully a soldier's honor and do not accept "society made me do it" defenses. Yet convictions can be hard to obtain because the units involved tend to cover up the facts.

Many supporters of the wars in question are happy to see as few convictions as possible. They worry that prosecutions will poison public sentiment. This concern is overblown. What matters most to most folks back home is whether their "boys" are fighting for a just cause and whether they are winning. If the answer to both questions is yes, the public will forgive a great deal of misconduct. Thus, celebrated war-crimes cases did not prevent American victory in the Philippines or British victory in South Africa. Nor was the My Lai massacre a turning point in the Vietnam War. By the time it was exposed in late 1969, support for the war was already in freefall because victory did not appear to be in sight.

Today, Americans' (and Iraqis') verdict on the war will not turn on what happened in Abu Ghraib or Haditha. More important is what is happening in Ramadi and Baghdad — major cities where the security situation has deteriorated over the last year. The Bush administration can weather the excesses of some soldiers; it cannot survive the perception that we are losing.

Instead of indulging in excessive self-flagellation, therefore, the Pentagon and the White House would be well advised to take decisive steps, such as sending more troops, to restore law and order.

Victory diminishes the significance of war crimes; defeat magnifies them into defining events.

Max Boot is a senior fellow at the Council on Foreign Relations. He wrote this commentary for the Los Angeles Times.