On the ninth day after Hamas overran more than 20 Israeli pastoral communities and army bases, killing more than 1,300 people and taking 150 hostages back to Gaza, Israel was a country on edge.

Israelis were girding with grim determination for what they widely see as a war of no choice after the attack on Oct. 7 — the deadliest day for Jews in Israel’s 75-year history and, officials say, since the Holocaust. They were awaiting an imminent ground invasion into the Palestinian enclave controlled by Hamas even as tensions escalated on the northern border with Lebanon, threatening a long and devastating conflict on several fronts.

All this is happening amid a total breakdown of trust between the citizens and the state of Israel, and a collapse of everything Israelis believed in and relied on. Initial assessments point to an Israeli intelligence failure before the surprise attack, the failure of a sophisticated border barrier, the military’s slow initial response and a government that seems to have busied itself with the wrong things and now appears largely absent and dysfunctional.

“We have woken to a terrible sobriety about whose hands we put our fate in,” said Dorit Rabinyan, an author in Tel Aviv. “All the time you said to yourself, ‘I am paying half of what I earn in taxes, but it is for security, national security, at least that.’”

“We thought we had military superiority, but there’s a feeling that someone up there forgot why he is there,” she added, referring to Prime Minister Benjamin Netanyahu.

After months of political and social turmoil over the divisive plans of Mr. Netanyahu’s ultranationalist government to curb the judiciary and undermine the country’s liberal democracy, shocked and grieving Israelis have come together to fight the battle and volunteer on the home front in hopes of eliminating the threat from Hamas on their doorstep and emerging stronger.

But on Sunday, the start of the workweek, the streets of Israel’s major cities were ominously quiet. Supermarkets in Jerusalem had run out of bottled water. Some of the last of the 30,000 residents of Sderot were fleeing the long-suffering city that lies two miles from the Gaza border.

In a country of nine million people, where most Jews serve in the army, everybody appears to know somebody who was caught up in the Hamas massacre or who is now on the front line. “Your hands tremble each time you answer your phone,” Ms. Rabinyan said, for fear of bad tidings.

The military high command has apologized for failing in its mission. Along with the so-called people’s army of conscripts, the military has mobilized 360,000 reservists, some of whom have continued to volunteer into their 50s.

A few months ago, at the height of the antigovernment protests over the judicial overhaul, thousands of reservists were threatening to quit, and many disillusioned Israelis were discussing leaving the country. Now, the few planes still landing in Israel over the past week have been filled with thousands of reserve soldiers returning for duty.

Public fury at the government has been compounded by Mr. Netanyahu’s refusal so far to openly accept any responsibility for the Oct. 7 disaster. He has made brief, televised statements but has not taken reporters’ questions. On Sunday, he met with families of hostages for the first time.

Many Israelis say they have not lost hope, putting faith in themselves, their army and the resilience they have shown in hard times in the past.

“The Israelis are built to function under pressure, though we never had a situation like this one,” said Tzadok Isuk, 74, the manager of a supermarket in Jerusalem where people have been panic-buying in recent days. Some shelves were empty because so many delivery drivers have been drafted into military service.

Mr. Isuk, who has a son in the security forces and two nephews along the Gaza border, said he had fought in all the country’s wars since 1967 but could hardly absorb what had happened. “It doesn’t make sense,” he said as a playlist of mournful Israeli folk songs were piped softly in the background.

Around the country, the atmosphere has been bleak as funeral after funeral has taken place. Hamas, the group that controls the Gaza Strip, continued firing rockets deep into Israel and the military has retaliated, pounding Gaza with punishing airstrikes. Hezbollah, the Lebanese Shiite organization, has also kept up a steady drumbeat of provocations in the north.

At dusk one day this past week, a ghostly silence had fallen over the center of Nahariya, a normally lively seaside town in Israel near the border with Lebanon. Most of the residents of the villages in the area had left for safer parts of the country.

And in the pastoral farmland along the border with Gaza, rows of tanks and armored vehicles were lined up this weekend in dusty fields among the cotton crops and orchards. The soldiers there said the mission was clear.

“To restore honor to Israel,” said Shai Levy, 37, a tank driver who in civilian life is a rabbi and teacher in a seminary. “The citizens are relying on us to defeat Hamas and remove the threat from Gaza once and for all,” he said, while stationed in a makeshift camp outside the gate of Be’eri, one of the worst-hit villages, where more than 100 people were killed.

“We’ve trained for years for this,” he said.

In Sderot, volunteers showed up to take residents to hotels in other parts of the country even before the authorities began an officially sanctioned evacuation.

Igor Fainstein, 44, an engineer, was trying to persuade his parents to leave on Saturday. A bullet hole was by the entrance of his ground-floor apartment, opposite a bus stop where Hamas gunmen had killed at least seven civilians on their way to a day trip at the Dead Sea.

“We will carry on living,” Mr. Fainstein said, before running for cover as two rockets from Gaza whooshed overhead without warning, followed by two loud explosions.

After the initial days of chaos and fog, the full horror of what happened has unraveled in increasingly gruesome detail over the past week, prolonging the shock and sharpening the trauma.

The front page of Yediot Ahronot, a popular daily, was filled on Sunday with photographs of 26 children being held hostage in Gaza, the oldest age 17 and the youngest 9 months. Other news media is filled with testimonies of atrocities and stories of valor.

Col. Golan Vach, the commander of the national search-and-rescue unit who arrived in Be’eri on the afternoon on Oct. 7, said he had found older people with their heads smashed and the body of a mother shot in the back as she tried to shield her baby. He said the head of the baby was severed from the torso of the burned remains.

In the twisted skeletons of two burned-out army jeeps, the colonel said, soldiers who battled the Hamas terrorists were found dead with their rifle magazines empty.

There is little empathy among Israeli Jews right now for the humanitarian crisis unfolding in Gaza, where more than 2,600 people have been killed, according to the Palestinian health officials.

Ms. Rabinyan is the author of the 2014 novel “All the Rivers,” a love story about an Israeli woman and a Palestinian artist based on her real-life romance, and a board member of several left-wing organizations opposing Israel’s occupation of the West Bank. But she said she had no room in her heart for the suffering of Palestinian civilians.

She was moving between hospitals and hotels housing survivors of the Hamas attacks, reading stories to children. “I know it’s not noble of me,” she said. “I know there is suffering on the other side, but the other side took hostages and slaughtered so violently, with so much passion, that my compassion is somehow paralyzed.”

For many Israelis, now is the time for fighting — and the reckoning with those responsible for the debacle will come later.

Nahum Barnea, a prominent Israeli commentator, wrote in Yediot Ahronot’s weekend edition, “We are mourning for those who were murdered, but the loss does not end there: It is the state that we lost.”

There is no telling how it will end. But the strong sentiment is that the Israel after Oct. 7 will not be the same as the Israel before.