How does this kind of story fit into the “Greatest Generation” narratives that became so prevalent in the 1990s, when I was a young man, and when journalist Tom Brokaw coined the term in his book of the same name? World War II was the “good war,” the one against a clear manifestation of evil, and, given the stakes for so many, a seemingly necessary war, too.

But Granddad, a serious New Englander with a voice like granite, was a pacifist, ready to counsel soldiers yet never prepared to accept that any war could be necessary or good. Love, for him, was always the highest virtue, a notion core to his Universalist faith. And while I’ve never quite been able to get my head around opposing the fight against the Nazis, I can see how his pacifism carried him through a lifetime of principle. He was a freedom rider, along with two of his children. He ran for Congress on a third-party “Peace Party” platform in Providence, R.I., during the Vietnam War. Pacifism was never passive but a call for him to active resistance.

Granddad wasn’t alone. In “War by Other Means: The Pacifists of the Greatest Generation Who Revolutionized Resistance,” journalist Daniel Akst argues that the modern progressive movement, wide-ranging in its causes and narratives today, has origins in the pacifist response to American involvement in World War II. In that period of intense pressure to join the fight against the Axis, a fight largely rendered from our present vantage, the men and women who chose resistance, prosecution, persecution, incarceration and public scorn reshaped the pathway of the American left in ways that would bear fruit over the following decades. Pacifists fought — and it is key for Akst that they framed their struggle as a nonviolent fight — segregation, detention of Japanese Americans and civilian bombing, and “most of all, influenced by Gandhi, they transformed their pacifism from a philosophy of wartime refusal into an active nonviolent system for confronting and defeating injustice.”

Akst organizes the book in loose chronological sections — before the war, as the first draft law is passed, after Pearl Harbor and so forth — but structures the book to follow key figures into and out of important episodes in the movement’s history. We see through the eyes of whichever individual he is following, keeping us at ground level. For example, he might bring the reader along with A.J. Muste into the formation of the Fellowship of Reconciliation, an interfaith peace organization, but has us leave that organization along with James Farmer, Bayard Rustin and George Houser to head to Chicago, where the peace activists built the Congress of Racial Equality. Early in the book, he takes us with David Dellinger from the football fields of Yale, a brawl after a game and then onto the rails, where Dellinger, a scion of privilege, bummed across the country along with fellow radicals like Don Benedict.

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Dellinger, Rustin and Dorothy Day are the pillars of this book, figures who provide Akst with “a snapshot in their pilgrimage as well as our own, an image filled with characters and events that speaks of their time but also contains clues to our own.” This is a way of explaining that the story will be necessarily fragmentary, with no one individual experience during the war fully fleshed out and too many stories left untold. Instead, Akst drags us into the flux of things, trying to show how one idea led to another, one radicalization inspired another, to build an organization that might fund a publication that might change the minds of a future leader. At its best, one gets the sense of generative force born from such intense intellectual, moral and religious pressure.

One of the best moments of analysis comes in the discussion of Day and “personalism,” a philosophy that “insisted that each of us, driven by love, had the power to change the world simply by changing ourselves.” It’s “mushy and idealistic,” Akst writes, but seeing the antiwar radicalism of the era as an “imaginative personalist enterprise … promulgated an enduring critique of materialism, militarism, racism, poverty, and government repression without erasing the moral and spiritual responsibilities we owe ourselves and others.” Personalism can succeed when the movement fails. As pacifists, personalism gives a pathway for heroism even when the struggle — the struggle to stop the war — is lost.

In “Mercy: Humanity in War,” historian Cathal J. Nolan takes another approach to finding heroes in war who do not fight — or at least those who find themselves in battle and choose to not kill, to save lives, to risk their own lives to help others or to try to simply do less harm. Where the pacifists were driven by absolute moral clarity, there’s nothing clear about the stories Nolan tells. Each is situated inside the hell of armed conflict, with acts of mercy shrouded in smoke, blood and horror, a “dehumanizing cacophony of the calamity that is war.” Still, Nolan convincingly argues, “mercy is a truer mark of heroic character in war,” because “the essence of genuine heroism is to choose and act rightly.”

For a book about compassion, though, “Mercy” is a museum of horrors. Nolan unflinchingly drags the reader through page after page of unsparing violence on land, sea and air. It’s not just that war is necessarily hell, but Nolan needs us to understand how often warriors choose to make it so. To advance their causes, soldiers rely on hate, dehumanization, torture, civilian suffering, indifference and more, and they do so on purpose. Nolan wants to suggest that it doesn’t have to be that way and that in fact recent military history (he moves mostly from the U.S. Civil War to the present conflict in Ukraine) is full of the heroism of mercy. He hopes soldiers will mimic the merciful not merely because compassion is good but because “acting compassionately will actually help you win.”

Does he succeed? I’m not sure. He does reveal story after story of men (and some women) who chose mercy, but it’s never clear why an individual might choose to save lives or whether a single good act can inspire others to act similarly. We encounter Christmas truces in the trenches followed by mass slaughter. A German admiral who tries to save some of the civilians whose boat he has sunk, only to respond to the complications (and counterattacks) by turning a “no prisoners” declaration into official policy. Abraham Lincoln sparing some of the participants in the Dakota War while overseeing a horrific mass hanging in Mankato, Minn. A medic saving the life of an Islamic State fighter who would go on to keep killing. Soldiers risking everything to rescue a wounded enemy who then dies anyway.

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On and on these examples pile up, and I worry that Nolan is too committed to showing the futility of mercy in the face of the grinder of war. For example, Nolan is repeatedly drawn to the Battle of the Hürtgenwald, where, in woodland hills in late 1944, the “U.S. Army was channeled by rolling topography and narrow roads to batter itself bloody against fixed positions, suffering one of its worst defeats.” During this conflict, Friedrich Lengfeld heard an American soldier crying out for help inside a German minefield. Lengfeld decided to help, holding up white flags and wearing Red Cross vests, but he stepped on a mine before he could reach the fallen G.I. He spent the next eight hours dying in incredible pain (American soldiers took him back to their casualty station but couldn’t help him). So instead of one dead soldier, now there were two.

Nolan doesn’t end the story there, though. In 1994, survivors of the battle went back to the Hürtgenwald and installed a small plaque dedicated to Lengfeld and his attempt to save an enemy. And that, for Nolan, is the outcome he’s looking for. Because — and this I think is core to the book’s argument — the power of mercy is not in the individual act’s outcome on a life or a battle, but in whether we tell these stories as examples of true heroism. “Honor is not enough. Valor is not enough. Law is not enough. Those whom we send to war also must be merciful,” he concludes.

I left these books neither fully committed to my grandfather’s model of pacifism nor confident in the ability of fighters to prioritize mercy over malice. But that’s not the point of either volume. Each author, perhaps in ways that might not be recognizable to the other, or at least the other’s subjects, finds heroism in actions that are about the individual person facing a choice. They, perhaps like my granddad, chose harder ways that often came with difficult consequences. But, of course, to sign up for the draft, to pull the trigger, these too come with consequences not only for the enemy but for the self — and, for my granddad, a religious man, despite or even because of his conflict with his very first church, possibly the soul. I wish I could ask him.

The Pacifists of the Greatest Generation Who Revolutionized Resistance

Melville House. 384 pp. $28.99