Kfar Aza, Israel

By the time I enter this community adjacent to the Gaza Strip, the Israeli army has removed most of the bodies. I am with a unit of the rescue organization Zaka, whose job is to retrieve parts missing from the bodies of the dead so that they can be made whole and given a proper Jewish burial.

The unit consists of civilians and military personnel, secular and Orthodox Jews. On a coffee break, they sit in a circle on plastic chairs on the patio of a sacked farm that serves as the unit’s headquarters. Some complain about their government’s negligence. One counters that no government can stop the madness of a mob.

The atmosphere of brotherhood contrasts with the recent months of civil struggle. Now, the only thing that counts is the holy task of combing through houses to recover a piece of blackened flesh, an intact foot still in its shoe, a trace of DNA, a bloodstain.

We freeze suddenly when someone finds the body of a jihadist that we fear may be booby-trapped. Then comes a moment of panic because it seems two terrorists might have just entered through a new breach in the security fence nearby, or the old one but now enlarged—no one knows.

We spot a drone in the sky, like a sparrow hawk. Mingling with its wasp-like buzzing are the sounds of dull explosions. A combat unit in assault gear emerges and takes its position. Some soldiers kneel; others climb to the roofs; still others move to the severed security barrier, from which appears a shower of sparks.

I am led into a house with shattered windows. Its inhabitants were murdered, their hands tied behind their backs, shot and in some cases finished off with a knife. I remain for two hours with nothing to do but listen to a surviving neighbor recount the attack. Over and over, he leads me through the rooms of this theater of torture.

The plaster ceilings chipped by shooting. The bullet-riddled walls. The beige sofa that an explosion raised off the ground and sent flying into the broken bay window. The parents’ room, with its unmade bed, hair curlers, worn slippers. The children’s room, with an open coloring book and a battery-powered cat meowing periodically. In the kitchen, an intact bowl of hot chocolate, a toaster, a bottle of cough syrup, a plush toy, an overturned laundry basket. And, at the end of a right-angled hallway, the safe room that the attackers opened by blowing it up with a grenade, leaving nothing but chunks of concrete, bloodied iron reinforcing and empty hinges opening and closing on nothing.

On the wall hangs a charcoal portrait of a 60-ish man with a billowy shirt, sleeveless vest, pipe, and soft hat pushed back from his forehead. I think of a farmer out of Steinbeck or an Israeli pioneer from a novel by A.B. Yehoshua or Amos Oz.

Kfar Aza and the other martyred places in this part of Israel—Sa’ad, Be’eri, Re’im—aren’t mere villages. They are kibbutzim, the distinctive rural communities of early Israel, the living remains of liberal Israel whose inhabitants are often among the most ardent advocates of peace with the Palestinians. This war pits Hamas against the kibbutz, the Islamist Einsatzgruppen against the faithful members of one of the few 20th-century utopias that haven’t broken into pieces.

Modern Israel was established in 1948, the same year I was born. I fly here as soon as I can, as I have done every time the country has gone to war since 1967. My first stops are Ashdod and Ashkelon, coastal cities north of the Gaza Strip, where sirens wail and the few drivers stop short in the middle of the road to tumble into the drainage ditch for shelter.

I take a detour east through Be’er Sheva, where a succession of helicopters, military and civilian, are bringing the wounded to the Soroka Medical Center at an awful pace.

Then I head back to Sderot, which, of all the cities of the south, is the most exposed whenever war breaks out. I realize that I have never seen it except under a hail of missiles.

What might Sderot look like at a time when its children are going to school and are not confined, as they are today, in the basements of buildings on Abargel Road, from which you can hear the whistle of rockets through the thick concrete? What is the face of Sderot when one doesn’t risk stumbling, in the middle of Menachem Begin Road, on the swollen remains of a jihadist felled in the last hours of the assault—his weapon still by his side, his exposed legs blackening, his body not yet covered, as others are further on, by an emergency blanket or a tarp?

And who is Yossi, 83, when he hasn’t spent the night in his basement with his grandchildren listening to the footfalls of the killers hunting for them above? They knew he was there—they called out his name and the names of his grandchildren, whom he silently implored, his finger to his lips, not to answer or to cry. Twice the killers came down and tried to open the latchless door against which Yossi braced himself with every ounce of his strength. What does he look like when he isn’t wearing the fierce, youthful look that his courage has given him?

This morning, Sderot is a dead city. Its streets are a web of deserted Via Dolorosas in which one wonders for whom the intense October sun is shining. The city’s fire chief was shot point-blank while fighting a blaze in a house where a handicapped couple was trapped. I attend his funeral at the firehouse, where sharpshooters, who are supposed to be guarding the entrance, take turns standing at the casket. The chief’s fellow firemen, their chiseled cheekbones contrasting with moist eyes in swollen sockets, unite in silent grief. They all seem to be saying that the Jews haven’t come to wage war but to pray, study, build libraries and sometimes put out fires set by evil men.

The ghost-town atmosphere, the dead shell of the police station that had to be destroyed to flush out the last terrorists—and, in front of its sagging facade, the odd spectacle of Gideon Levy, Haaretz journalist and star of the peace camp, in friendly conversation with a soldier in a kippah—all of it breaks the heart.

No one can predict much about the Israel Defense Forces’ land offensive—whether it will be massive or targeted, long-term or temporary, or even whether it will happen at all.

But in Jerusalem I meet President Isaac Herzog. In principle, he has only symbolic power. But his personal aura, combined with what many Israelis see as Prime Minister Benjamin Netanyahu’s disgrace, has turned him into a central figure on the national political scene.

Not once did Mr. Herzog mention “revenge.” As we strolled in the statue garden of the presidential residence, where we stopped before the bust of Shimon Peres, this former lawyer, steeped in Jewish culture and humanism, embodied the spirit of moderation and wisdom that I have always found in him. But I sense that he is worried, impatient. He has a three-day beard and, behind the rimless glasses of a man of study and knowledge, an insomniac expression that I have never seen.

He calls the Oct. 7 massacre the “worst tragedy in Israel’s young history” and says Hamas is “neither a resistance group nor a national liberation movement, but rather a twin of the Islamic State.”

The Western world faces a “moment of truth,” he insists with an unfamiliar but well-contained touch of anger in his voice. Does the West understand that it is not possible to refrain from punishing those who “slit children’s throats” at the Tribe of Nova music festival? Will the West join Israel in doing what it takes to ensure that “those who gave the orders for this infamy, whether they are in Gaza, Doha or Tehran, will never be able to do so again”?

In Tel Aviv, on a day of high alert when the Iron Dome was in ceaseless operation, I see former Deputy Prime Minister Benny Gantz, a brigadier general with an impeccable record, a legendary parachutist who in 1991 was responsible for Operation Solomon, which repatriated the Jews of Ethiopia.

On the day we meet, he is still one of the leaders of the opposition. He hasn’t decided whether to accept Mr. Netanyahu’s invitation to participate in a national unity government. He knows that if he does accept the offer, if he lends his political adversary the immense credibility he enjoys within the Israeli army, he will be running a personal political risk.

But this is no longer “about individuals,” he says, his husky voice seeming to strike through his teeth. He swore to himself that if he joined the cabinet he would “leave it again the very second the war was won.” But before that can happen, the war will have to be waged. One must keep in mind, he muses, that there are solemn moments—today is one of them—when Israel, laboring under the twin pressures of external enemies and internal discouragement, faces an existential threat.

He says goodbye, then pauses to relate a series of wrenchingly beautiful anecdotes: A retired general friend hopped into his car, revolver in hand, to save a family trapped in its kibbutz. An officer planning the liberation of another kibbutz was informed that his own son was among the first killed. He took 10 minutes to weep, collected himself and resumed command.

“The Palestinians are not Israel’s enemy,” Mr. Gantz says. “It is Hamas that must be destroyed.” At the edge of the Gaza Strip, IDF units position themselves to do that job. With their mine-clearing bulldozers, their real and decoy tanks, and their ranks of reservists, they are preparing to go into action.

The grinding of the tank treads grows louder. With menacing patience, helicopters whirl overhead in the blue sky. A mass of men and women have come from every nation of the world to stand in a forest of flags fluttering in the breeze of a warm afternoon that seems endless: They are gathering to confront one of the most tragic tests in the history of the state of Israel.

Under the drumbeat of human voices muffled by the freshly tamped earth and sand floats a series of questions to which they don’t always know the answers but that they are determined to face.

Will they succeed in saving both their nation and the hostages, whose number grows from hour to hour and whose cause is sacred here? If they succeed, will they remain faithful to the Jewish morality that leads them to treat captured jihadists as decently as Jewish children, as I witnessed at the emergency care center in Be’er Sheva?

What of the famous code of purity of arms, the Tohar HaNeshek, that was so important to Israel’s pioneers? This creed explains why one finds lawyers embedded with the soldiers of every IDF unit—unarmed men who have the power to question and even suspend any order they deem inconsistent with international law and ethics. How will these imperatives fare in the face of an adversary whose cynicism is boundless, that makes hostages of its own people and doesn’t hesitate to use them as human shields and grist for propaganda?

Will Egypt—self-described ally and sister of the Palestinian people—open its border to the hundreds of thousands of Gazans asked to leave the northern zone to protect themselves from the fighting?

And these young Israeli soldiers, fervent and tormented—will they return alive from the Gaza that lies before them like a dark mass lit up from afar by incoming and outgoing rockets?

Among the soldiers are men and women of the left and of the right; supporters of Mr. Netanyahu as well as opponents who recognize him only reluctantly as their commander in chief; Jews who wear the Tefillin and Jews who do not. I have heard none of them deny that this war is just and must be won.