AMNA NAWAZ: The United Nations says that more than 360,000 Gazans who fled to Rafah have now been forced to flee again, as Israeli troops attack sectors of the city in a bid to rout Hamas.

Also in Rafah today, the first foreign U.N. staffer was killed by Israeli troops.

More than 100 Palestinian U.N. staff have been killed since October 7.

Nick Schifrin has our report.

NICK SCHIFRIN: A city that's been teeming with the displaced is now slowly being deserted.

A quarter of the 1.3 million Gazans who fled here are now packing everything their cars or bikes can carry and fleeing again.

Fathia Ahmed is among the last to leave.

FATHIA AHMED, Displaced Palestinian (through translator): I don't have a choice, like everyone else.

Everyone left, so I am doing the same.

What should I do, stay alone?

I am scared to stay alone.

NICK SCHIFRIN: Many have been displaced to what is essentially the beach, piling their lives upon a pile of sand.

Meet the Zatar family.

This is their third home, as it were, since the war began.

The children have kept their smile, but their mother Amenah's has vanished.

AMENAH ABU MOAMAR, Displaced Palestinian (through translator): I can't find a tent to set up for me and my children.

They are suffering underneath the sun.

Its heat has burned them, and they are ill. NICK SCHIFRIN: Israel is ordering Rafah evacuated because the IDF says Hamas' final four battalions fight from there, including with mortars last weekend that killed four Israeli soldiers and blocked humanitarian aid.

AVI HYMAN, Israeli Government Spokesman: Let's make it clear.

If we don't destroy the last four battalions of Hamas in Rafah, we will have lost the war.

NICK SCHIFRIN: And now Israel has launched new raids on what it calls Hamas terrorist infrastructure in Central and Northern Gaza, areas that Israel long ago cleared.

BRIG.

GEN. JONATHAN SHIMSHONI (RET.

), Israeli Defense Forces: What we're seeing is a kind of "Sorcerer's Apprentice"-type dynamic.

The units devolved into small guerrilla teams, and they don't require any centralized command and control.

NICK SCHIFRIN: Retired Brigadier General Jonathan Shimshoni had a 50-year career in the military and is now with Commanders for Israel's security.

He says, in Central and Northern Gaza, Hamas is able to reconstitute because there is no one there to stop them.

BRIG.

GEN. JONATHAN SHIMSHONI: Israel has not created an alternative, so there is no alternative there, and Hamas is exploiting the vacuum.

NICK SCHIFRIN: Today, National Security Adviser Jake Sullivan said Israel must look beyond individual military victories to find a political strategy.

JAKE SULLIVAN, U.S. National Security Adviser: There needs to be more attention that piece of it, lest we end up in a circumstance where Israel conducts a military operation, kills a bunch of Hamas guys, also creates some harm to innocent civilians caught in the crossfire, and then terrorists come back, as we have seen them come back in Gaza City and Khan Yunis and other places.

We want to avoid that outcome.

BRIG.

GEN. JONATHAN SHIMSHONI: The army has been saying for months now, tell us what it is that you really want to achieve in Gaza.

I mean, what is the political diplomatic outcome that you envision, so we know what to pursue?

So, as the Cheshire Cat said, if you don't tell me where you want to go, I can't tell you how to get there.

NICK SCHIFRIN: But those strategic debates feel detached from the trauma.

Today is Israel's Memorial Day, more raw than ever, especially at the site of the worst single attack of the worst terrorist attack in the country's history, the Nova Music Festival.

EITAN REFAELI, Israel: Sad.

Sad.

The sky is crying with us.

The rain was all around.

I feel bad.

I feel very, very, very sad, very sad about what happened here in this place, in this area.

NICK SCHIFRIN: Today, Prime Minister Benjamin Netanyahu said the soldiers who died fighting died for an existential cause.

BENJAMIN NETANYAHU, Israeli Prime Minister (through translator): It's us or them, Israel or the monsters of Hamas.

It's existence, freedom, security, and prosperity, or annihilation, massacre, rape, and enslavement.

We are determined to win this fight.

But the price we are paying and the generations before us paid is heavy.

NICK SCHIFRIN: The war is heavy for everyone looking for light to pierce the darkness.

For the "PBS NewsHour," I'm Nick Schifrin.