Israeli artillery and helicopters have been pounding Gaza for more than a week
By Jeremy Bowen
BBC Middle East editor, Israel-Gaza border
Along the Gaza border, fields that were full of tanks and troops are almost empty.
The men and machines have moved into Gaza, and throughout the day the sounds of what they were doing rumbled back into Israel.
At the end of the first 24 hours of the ground offensive fresh Israeli troops were heading for Gaza. Helicopters were clattering towards Gaza from Israel.
Observers could hear the sound of the engine, a pause, and then the thunder of another explosion.
In the Israeli border town of Sderot more people were on the streets during the day than a few days ago.
They were feeling less tense now that Israel had sent soldiers in.
Israel's justification for what it is doing is the need to protect its citizens in Sderot and the other towns within rocket range of the Gaza Strip.
Ghost of 2006
Other factors are at work though. The Israeli army wants to lay the ghost of what is widely seen in Israel as its failure during the Lebanon war of 2006.
Military sources say that their soldiers are now better trained. And they are managing public expectations differently.
In 2006 Israel said that it was fighting to stop missiles hitting northern Israel.
That meant that if its Hezbollah opponents could still launch missiles on the last day of the war they could say that they had won. And that is what happened.
On the day the ceasefire came into effect, Hezbollah fired more missiles at Israel than on any other day of the war.
Hamas wants to emulate Hezbollah's performance in 2006. So Israel has been careful since the ground offensive started not to say that their soldiers were fighting to stop every rocket.
Instead senior Israeli officers have told journalists that the aim is to decrease the rocket fire and make it less accurate.
Israel wants to be in a position to dictate the terms of the ceasefire when it comes.
Israel also believes its actions in Gaza are sending a message to its enemies elsewhere in the Middle East - and especially to Hezbollah in Lebanon.
The Israeli army wants the Gaza campaign to restore what it calls its deterrent capacity.
In 1967 the Israeli armed forces seemed invincible after they beat Jordan, Egypt and Syria in six days.
But after 2006, when they could not stop an irregular force of guerrillas firing into their territory, they were much less impressive.
Israel hopes that its actions in Gaza will restore their army's power to scare and to bully any potential enemies.
Life goes on
I am writing this at the cafe at the Yad Mordechai service station, on a road junction between Sderot and the main crossing into Gaza.
Israeli tanks have been massing outside Sderot
At the moment the customers are mainly Israeli soldiers and journalists. Israel is refusing to let international journalists into Gaza, defying a ruling from the Israeli supreme court, so many of them are stuck here.
Yad Mordechai has become one of the surrealistic places that always emerge in war zones.
The scene here is strange not because it is abnormal, but because it is so normal.
The staff are friendly, the place is clean, the food is good, and the news is on big screens. Yet only a couple of miles away Israel and Hamas are fighting a war.
At the best of times the contrast between the lush farmland in this part of Israel and the ravaged landscape of northern Gaza is very strong.
Tonight though, the noise, the dirt and the smell of war just down the road, on the other side of Israel's border defences, must be overwhelming.
Occasionally there are reminders that a war is going on. The windows just rattled after something exploded not too far away. The soldiers and the journalists glanced at each other, and went back to their food.
It is not hard to imagine how different it must be in Gaza, how terrifying it must be to be a parent stuck somewhere in the inferno trying to protect and reassure terrified children.
This is from its latest bulletin from the Gaza office of the UN office for the coordination of humanitarian affairs:
"The military incursion compounds the humanitarian crisis following more than a week of shelling and an 18-month long blockade of the territory.
"There is an increased threat to civilians due to combat in densely populated urban areas.
"Hospitals continue to be overstretched because of the large number of casualties that have accumulated since the beginning of Israeli attacks, and ambulances and medical personnel face difficulties in accessing casualties.
"Electricity and telecommunications are down over much of the Gaza Strip. Food distributions have been suspended and all crossing points remain closed."
Israel says it has no alternative. It says that no other country would tolerate attacks on its civilians, and would react in the same way.
Israel's actions have provoked fury in the Arab world
Its actions, it insists, are entirely legitimate acts of self-defence. Its ally the United States agrees strongly.
But using so much force and killing so many Palestinians could be storing up problems for the future.
What is happening is being broadcast live by satellite to millions of households across the Middle East. It makes it much harder for those Arabs who believe in a negotiated settlement with Israel.
On the Palestinian West Bank, separated from Gaza by Israeli territory, there was another day of demonstrations. Talk of a peace process sounds hollow on the streets of the West Bank.
For the last 18 months Israel and its allies have agreed to continue isolating Hamas and to allow only the most basic essentials into Gaza.
It was a policy which reflected their total rejection of Hamas's ideology and actions.
It was easier to stick to that policy than to make serious attempt to address the problems of Gaza, the Palestinians and Israel.
Diplomats and leaders on all sides should have done better. They might have avoided this war.
But that did not happen and it is too late now, at least until this round of bloodletting is over.