Soldiers have long been subjected to invidious generational comparison. It's a military rite of passage for new recruits to hear from old hands that everything from boot camp to combat was tougher before they arrived. The late '90s coronation of the "Greatest Generation"—which left many Korean War and Vietnam War veterans scratching their heads—is only the most visible cultural example.

Generational contrasts are implicit today when casualties in Iraq are referred to as light, either on their own or in comparison to Vietnam. The Center for Strategic and Budgetary Assessments, for example, last July downplayed the intensity of the Iraq war on this basis, arguing that "it would take over 73 years for U.S. forces to incur the level of combat deaths suffered in the Vietnam war."

But a comparative analysis of U.S. casualty statistics from Iraq tells a different story. After factoring in medical, doctrinal, and technological improvements, infantry duty in Iraq circa 2004 comes out just as intense as infantry duty in Vietnam circa 1966—and in some cases more lethal. Even discrete engagements, such as the battle of Hue City in 1968 and the battles for Fallujah in 2004, tell a similar tale: Today's grunts are patrolling a battlefield every bit as deadly as the crucible their fathers faced in Southeast Asia.

Economists like to quote statistics in "constant dollars," where they factor in historical inflation rates to produce statistics that allow for side-by-side comparison. Warfare is more complex than macroeconomics, but it is possible to produce a similar "apples to apples" comparison for casualties across conflicts. In a recent article for the New England Journal of Medicine, Atul Gawande (a former Slate contributor) concluded that improvements to military medicine since Vietnam have dramatically reduced the rate at which U.S. troops die of wounds sustained in combat. The argument follows a 2002 study that tied improvements in U.S. civilian trauma medicine to the nation's declining murder rate. While firearm assaults in the United States were rising, the murder rate was falling, largely because penetration wounds that proved fatal 30 years ago were now survivable. Thus, today's murder rate was artificially depressed in comparison to the 1960s.

Gawande applied the same methodology to U.S. casualty statistics in previous wars, arriving at a "lethality of wounds" rate for each conflict. In World War II, 30 percent of wounds proved deadly. In Korea, Vietnam, and the first Gulf War, this rate hovered between 24 percent and 25 percent. But due to better medical technology, doctrinal changes that push surgical teams closer to the front lines, and individual armor protection for soldiers, this rate has dropped to 10 percent for Operation Iraqi Freedom for all wounds. For serious wounds that keep a soldier away from duty for more than 72 hours, the mortality rate is now 16 percent. Simply, a soldier was nearly 1.5 times more likely to die from his wounds in Vietnam than in Iraq today.

This disparity between the "lethal wound" rates has profound implications. Analogy is a powerful tool for perspective, and Vietnam still reverberates, but the numbers must reflect the actual risks. In 1966, for example, 5,008 U.S. servicemen were killed in action in Vietnam. Another 1,045 died of "non-hostile" wounds (17 percent of the total fatalities). Since Jan. 1, 2004, 754 U.S. servicemen and -women have been killed in action in Iraq, and 142 more soldiers died in "non-hostile" mishaps (16 percent of the fatalities, similar to Vietnam). Applying Vietnam's lethality rate (25 percent) to the total number of soldiers killed in action in Iraq this year, however, brings the 2004 KIA total to 1,131.

The scale can be further balanced. In 1966, U.S. troops in Vietnam numbered 385,000. In 2004, the figure in Iraq has averaged roughly 142,000. Comparing the burden shouldered by individual soldiers in both conflicts raises the 2004 "constant casualty" figure in Iraq to 3,065 KIA. Further, casualties in Iraq fall more heavily on those performing infantry missions. Riflemen—as well as tankers and artillerymen who operate in provisional infantry units in Iraq—bear a much higher proportion of the risk than they did in Vietnam. In Vietnam, helicopter pilots and their crews accounted for nearly 5 percent of those killed in action. In Iraq in 2004, this figure was less than 3 percent. In Vietnam, jet pilots accounted for nearly 4 percent of U.S. KIAs. In 2004, the United States did not lose a single jet to enemy action in Iraq. When pilots and aircrews are removed from the equation, 4,602 ground-based soldiers died during 1966 in Vietnam, compared to 2,975 in Iraq during 2004.

Perhaps a more significant change is the marriage of technology with doctrinal changes. In World War II, Korea, and Vietnam, attrition warfare dominated infantry operations. Today's commanders fight differently, first shaping the battlefield with air power and artillery, then committing ground troops to attack enemies weakened by these barrages or bypassing them altogether.

But some situations defy the effects of technology and force infantrymen to fight much the way they did 30 years ago. In urban areas, most significantly, buildings hide Iraqi insurgents from aerial observation and protect them from incoming ordnance. Cities also make it easy for small bands of insurgents to hide among the civilians. In Fallujah, the Iraqi insurgents who burrowed into the city had to be pried out by American infantry—just as the Marines did when they fought to retake Hue City in 1968.

The Hue comparison is illuminating. In Hue, three Marine battalions (roughly 3,000 men) plunged into a vicious house-to-house fight with 12,000 North Vietnamese, ultimately routing them after suffering harsh losses. In April 2004, three Marine battalions attacked several thousand terrorists in Fallujah and were days away from taking the city when the White House called off the attack. In November, three new Marine battalions joined two Army mechanized infantry battalions in a sweeping attack to retake the city. They succeeded, although outbreaks of fighting continue. While the North Vietnamese fought a coordinated defensive battle for Hue City until they were annihilated, the terrorists in Fallujah fought in small packs, hiding among the tens of thousands of structures in the "city of mosques." In the three-week battle for Hue, 147 Marines were killed and 857 wounded. In the twin battles for Fallujah, more than 104 soldiers and Marines have been killed and more than 1,100 wounded in a battle that will continue to take lives, like the three Marines who encountered yet another pocket of fighters last week.

Hue and Fallujah provide one of the best generational comparisons of combat because both battles unfolded similarly. Without controlling for any of the advances in medical technology, medical evacuation, body armor, or military technology, U.S. losses in Fallujah almost equal those of Hue. If you factor in the improvements in medical technology alone, then the fight for Fallujah was just as costly (or maybe more so) as that for Hue, as measured by the number of mortal wounds sustained by U.S. troops.

That today's fighting in Iraq, by these calculations, may actually be more lethal than the street fighting in Vietnam should not be taken lightly. Vietnam was marked by long periods of well-fought, sustained combat but little perceptible gain. Volunteers outnumbered conscripts by a 9-1 ratio in the units that saw combat during the war's early days in 1966, and at first they enjoyed the support of a country that believed in their cause. But as the burden widened and deepened, and conscripts did more of the fighting and dying, the country's faith evaporated. Today's burden is not wide, but it is deep. Communities such as Oceanside, Calif., home to Camp Pendleton and the 1st Marine Expeditionary Force, have suffered tremendous loss during this war—nearly one-quarter of U.S. combat dead in 2004 were stationed at Camp Pendleton. Military leaders should be mindful of this fact: To send infantrymen on their third rotations to Iraq this spring is akin to assigning a trooper three tours in Vietnam: harsh in 1966 and a total absurdity by 1968.

Critics of the war may use this analysis as one more piece of ammunition to attack the effort; some supporters may continue to refer to casualties as "light," noting that typically tens of thousands of Americans must die in war before domestic support crumbles. Both miss the point. The casualty statistics make clear that our nation is involved in a war whose intensity on the ground matches that of previous American wars. Indeed, the proportional burden on the infantryman is at its highest level since World War I. With next year's budget soon to be drafted, it is time for Washington to finally address their needs accordingly.