GEOFF BENNETT: Today, Israel's military allowed humanitarian aid into Gaza for the first time in nearly three months, as the leaders of Britain, France and Canada threatened to sanction Israel if it didn't provide more assistance.

Israel also ordered Gaza's second largest city evacuated as part of a new ground operation.

Here's Nick Schifrin.

NICK SCHIFRIN: In Rafah today, a new campaign to reoccupy Gaza.

The operation is named for a biblical leader who annihilated his opponents.

Israel's now vowing to clear Hamas once and for all and hold territory, all of Gaza's territory, Prime Minister Benjamin Netanyahu said today.

BENJAMIN NETANYAHU, Israeli Prime Minister (through translator): We're going to take over all areas of the Strip.

That's what we're going to do.

NICK SCHIFRIN: And so excavators march into battle with a mission to flatten Gaza.

And an already destroyed city, Rafah, is reduced to further rubble.

In the last month, Israel has expanded what it calls a buffer zone along the Gaza border from hundreds of feet to more than a mile and enlarged corridor that bisects Gaza.

Today, it ordered the evacuation of Gaza's second largest city and says it will move through Khan Yunis toward the sea.

Israel controls about a third of Gaza and is pushing the population into shrinking pockets outside of IDF control.

ASSAF ORION, The Washington Institute for Near East Policy: We are now seeing Israel moving to create some kind of an inhabitable hellscape by demolishing the remaining buildings that Hamas is still using.

NICK SCHIFRIN: Assaf Orion is a fellow at the Washington Institute whose final posting as a brigadier general was head of the Israeli military's strategic planning.

ASSAF ORION: If you are looking for absolute and total victory, it calls for very extreme measures, which means that the IDF will need to stay and hold this territory, devoting and investing a lot of units, a lot of forces, a lot of expenses in blood and treasure.

NICK SCHIFRIN: Part of Israel's efforts to strangle Hamas has been to withhold aid, until today.

For the first time in more than 11 weeks, aid trucks left a border crossing and entered Gaza, in part because of U.S. pressure, Netanyahu admitted today.

BENJAMIN NETANYAHU (through translator): Our greatest friends in the world come to me and tell me, we are giving you all the assistance to complete the victory.

There's one thing we cannot stand.

We can't accept images of hunger, mass hunger, and we won't be able to support you.

Therefore, in order to achieve victory, we must somehow solve the problem.

NICK SCHIFRIN: And the problem is mass hunger.

An umbrella organization of U.N. and international humanitarian groups declared that nearly half-a-million people face catastrophic hunger and are at risk of famine, especially Gaza's most vulnerable.

CLEMENCE LAGOUARDAT, Program Coordinator, Oxfam: We have children that have been deprived of proper food for more than 70 days, and they are one of the first victim of starvation.

NICK SCHIFRIN: Clemence Lagouardat is Oxfam's program coordinator, who recently returned from Gaza.

CLEMENCE LAGOUARDAT: What I have seen is total destruction of the Gaza Strip.

It's to a scale that is different to imagine until you see extremely young children that are just too tired and that are consuming their whole energy to just basically survive and that don't even have the strength to cry anymore.

NICK SCHIFRIN: Earlier this year, during a cease-fire, every day, nearly 600 trucks entered Gaza.

The U.N. called today's nine trucks a drop in the ocean.

CLEMENCE LAGOUARDAT: How do you choose?

How do you prioritize?

This is quite impossible, and it's not going to solve anything about the situation on the ground.

NICK SCHIFRIN: And it's not only food.

The daily displacement is multigenerational, sons supporting mothers, uncles pushing nephews.

Majid Al-Bareem flees his home with his dead brother's son and his earthly possessions.

His mother, Wafaa Al-Bareem, struggles to counsel a hungry grandchild.

WAFAA AL-BAREEM, Displaced Gazan (through translator): When a child comes and tells me, "Give me a piece of bread, grandma," sometimes, I have one loaf of bread.

I give it to them and I sleep hungry.

By God, we are tired.

We are dying slowly.

They are besieging us, no food, drink or anything.

NICK SCHIFRIN: The displacement is designed to facilitate a new Israeli-backed American aid group to distribute aid only to vetted Gazans.

It's an effort that international aid groups oppose.

CLEMENCE LAGOUARDAT: It seems that they will be operating in a system that is pushed by Israel and that is basically instrumentalizing humanitarian assistance,that is politicizing it and that is serving a purpose, a political and military purpose.

NICK SCHIFRIN: In the meantime, there is so much loss.

In Jabalia, they mourned a child, one of 500 people that Gaza health authorities say have been killed in the last eight days, and the ruins strewn as far as the eye can see.

For the "PBS News Hour," I'm Nick Schifrin.