John McCain's widely irresistible story does not begin with his valiant record as a prisoner of war. Nor is its most compelling aspect his role in bringing about an end to the punitive US embargo against Vietnam, although both accomplishments have stirred admiration in unlikely breasts, including mine. Rather, the episode that starts the McCain saga is one that few, including the senator himself apparently, have much reflected upon, yet it points to the most important - and troubling - aspect of this man's character. And that event bears comparison to another that occurred on the same day, launching an opposite saga.

On Oct. 26, 1967, McCain flew his A-4E Skyhawk, a single-seat attack bomber, toward a target in North Vietnam. His story begins when a surface-to-air missile hit the warplane above Hanoi, with well-known devastating results. But to understand the meaning of McCain's experience, other events just before and after must be considered, for that month was the pivot on which the entire arc of America's war in Vietnam turned.

By the beginning of that autumn, it had become clear to many military analysts that the war was being lost, and, in particular, that the air war was boosting North Vietnamese resolve, instead of undercutting it. That led Robert S. McNamara to turn against the war he had begun, and he now urged a bombing halt. ''The sole strategy for knocking the North Vietnamese out of the war from the air, McNamara concluded,'' as Stanley Karnow summarizes it, ''would be some form of genocide.'' Or, as McNamara himself put it, ''the virtual annihilation of North Vietnam and its people.''

In late October, Lyndon Johnson decided against McNamara, and ordered an escalation of the bombing. He approved, in Karnow's words, ''air strikes against 57 new North Vietnamese targets - nearly half of them in heavily populated areas ...'' And one of the first pilots given that mission was McCain.

The target toward which he so fatefully flew on Oct. 26 was, in the phrase of his biographer Robert Timberg, a ''previously off-limits'' power plant. The civilian infrastructure of Hanoi was now to be hit. McCain was an instrument of Johnson's escalation, which would quickly be exposed as the most terrible miscalculation of his presidency. Within weeks, McNamara would be out, and Eugene McCarthy would be in as a candidate for president.

Soon thereafter, Johnson, declining to run for reelection, would attempt to reverse his expansion of the air war, but a savage momentum had been unleashed. The most immoral aspect of America's war was then reified in the half-blind, ever more futile bombardment from the air, which would continue for five more years.

The imprisoned McCain could be expected to have no qualms about the air war, and he had none. His courageous clinging to an ideal of national honor is what endears him so widely. Yet, given the literal and symbolic significance of his place in the avant-garde of the strategic blunder - and moral catastrophe - that the escalated air war became, is it unreasonable to ask now for some reconsideration of a deeper meaning of honor?

McCain as the beloved icon of personal honor has reinforced a general American reluctance to face the national dishonor of American war-making, and he himself shows little or no ability to think deeply on this most crucial subject. That is why McCain's responses to contemporary questions of military policy, from Kosovo to the Missile Defense Shield, are so shockingly hawkish, far more appropriate to a young fighter jock than to a would-be statesman. He is an icon of escalation.

Consider, in contrast, the story of another young military man who specialized in ''killing from a distance,'' as his biographers Murray Polner and Jim O'Grady put it. He was an artillery spotter whose big guns shelled German-occupied cities during World War II, but ''the vast accidental cemeteries'' that he saw as his handiwork after the war changed him forever. And, as fate would have it, this veteran responded to Johnson's escalation on the same day that McCain did, but differently. On Oct. 26, 1967, he drew blood from his own arm, and then, the next day, with three others, he poured that blood on draft files at the Custom House in Baltimore - the first of what would be a dramatic escalation of peace movement protests.

That war veteran's name was Phillip Berrigan, and his time in prison for those protests would overlap with McCain's, and go on. After Vietnam, Berrigan's became a voice crying in the wilderness of unchecked American nuclearism.

Today, while McCain runs for president, the 76-year-old Berrigan is in jail in Baltimore again, awaiting trial for the December crime of having hammered, and once more poured his own blood, this time on the fuselage of an A-10 bomber at an air base in Maryland. The A-10, used in Iraq and Yugoslavia, fires ''depleted uranium'' weapons, which generate radioactive dust and represent another US escalation. Escalation forever.

The war protester and the war hero began their roles in this drama on the same day, but while Berrigan understands the American war story for the tragedy it is and lives accordingly, McCain sees it as an epic romance. Berrigan, in jail, is the truly free man, while McCain remains imprisoned in an unexamined sense of martial honor, which, in a president, would be truly dangerous.

James Carroll's column appears regularly in the Globe.

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