Did Israel – or its enemy, Hamas – commit war crimes during 22 days and nights of aerial assault, rocket launches and ground fighting in Gaza? In one sense the question is academic, because Israel will not recognise the conflict as an international one, and has not signed the 1977 Geneva protocol designed to apply to the victims of internal conflicts. But international lawyers say general principles can be drawn from the laws of war, which may have been violated in several ways.

The main issues are these:

Proportionality

Download the new Independent Premium app Sharing the full story, not just the headlines

Up to 10 times as many Palestinians were killed as Israelis. The Palestinian Ministry of Health says 1,314 Palestinians were killed, of whom 412 were children or teenagers under 18, and 110 were women. On the Israeli side, there were 13 deaths between 27 December and 17 January, of whom three were civilians killed by rockets fired from Gaza. Of the 10 soldiers killed, four were lost to "friendly fire".

Even if the Palestinian figure is disputed, it is clear that the death toll was massively higher for Palestinians than Israelis. Proportionality is not simply a matter of numbers, however. There will also be a debate over whether the destruction wrought by Israel's huge land, sea and air arsenal was proportionate to the threat posed by Hamas militants to civilians – itself also a violation of international humanitarian law.

With foreign journalists barred from Gaza by Israel throughout the war, it is especially hard to come by hard information on the exact circumstances in which all civilian casualties were caused. But unofficial comment from senior military officers in the Israeli media have suggested that a deliberate choice was made to put the protection of its soldiers first, and that of civilians second. If true, it appears to have been successful, but even if it wasn't, the "collateral damage" inflicted on civilians appears to have significantly exceeded the norms even of previous Israeli operations in Gaza, suggesting looser rules of engagement for military operations.

The head of Human Rights Watch, Kenneth Roth, pointed out that there was an "expansive" definition of military targets, to include civilian government offices, police stations and the parliament building, on the grounds they at least indirectly helped Hamas.

Firing into urban areas

Israeli forces did not penetrate into the heart of Gaza City or Khan Yunis. But many of the areas where they deployed their forces were heavily built up. Probably the most lethal incident was the 6 January mortar attack that hit the UN school being used as a shelter for hundreds who had fled their homes in the northern Gaza town of Jabalya. It killed 30 straight away, and an estimated 13 more died from their critical injuries in subsequent days.

Israel's initial claim in this and several other incidents was that it was responding to fire from Hamas. The militants could be at fault for "locating military objectives within or near densely populated areas", in the words of the Geneva Conventions. But the conventions also forbid any attack expected to cause death or injury to civilians "which would be excessive in relation to the concrete and direct military advantage anticipated" – a rule Israel is accused of breaking several times.

Though it fortunately caused no deaths and only two injuries, the incident in which shells containing phosphorus hit the UN Relief and Works Agency headquarters – where many were also sheltering – was almost as high profile. Not only did they set fire to food and medical supply warehouses, they landed as the UN Secretary-General, Ban Ki-moon, was holding meetings with Israeli leaders. UN chiefs vigorously denied Israeli suggestions made in the media, though apparently not to the UN itself, that Hamas gunmen had been sheltering in UN premises. In the first case Chris Gunness, UNRWA's chief spokesman, revealed that diplomats had been told by the Israeli authorities that Hamas was not operating from the school. And in the second, Mr Ban said that Israel's Defence Minister, Ehud Barak, had acknowledged a "grave mistake".

White phosphorus

White phosphorus – which can cause horrific injuries, and is heavily restricted in international law – is now widely accepted to have been used by Israel in this war at several locations. Dating originally from the First World War, white phosphorus and its distinctive plumes of white smoke can legally be used to mark objectives, spread smoke for concealment or set fire to military targets, but not in civilian areas. Israel first denied using it at all, then claimed it was being used only in uninhabited areas, and then last week announced an investigation into its use.

A high school student Mahmoud al-Jamal, 18, was lucky to have been hit by phosphorus shelling during the third week of the war. By the time he reached the care of Gaza City's Shifa hospital, unconscious and severely burned in his left arm, legs and chest, the head of the burns unit, Dr Nafez abu Shaban knew the only hope of saving him lay with surgery. Shifa had no experience of it before 27 December, but "by the last week of the war we knew that we had to get the patient to the operating room and excise all the burnt tissue".

Daily coronavirus briefing No hype, just the advice and analysis you need Enter your email address Continue Continue Please enter an email address Email address is invalid Fill out this field Email address is invalid Email already exists. Log in to update your newsletter preferences Register with your social account or click here to log in I would like to receive morning headlines Monday - Friday plus breaking news alerts by email Update newsletter preferences

Mahmoud was running from the heavy fighting between Hamas gunmen and Israeli forces in the southern Gaza city district of Tel Al Hawa when a shell dropped in front of him. "I could feel my whole body burning," he said. "I fell and asked someone next to me to help. But he was dead. Then I fainted." Part of his body was still smouldering when he was being anaesthetised in theatre. "A piece extracted itself from his body and burned the anaesthetist on his chest," said Dr Shaban. Mahmoud will live; unconfirmed estimates are that dozens of others burned by phosphorus have not survived.

Dime bombs and other unusual weapons

While the vast majority of Palestinians were killed by conventional weapons, a Norwegian doctor, Erik Fosse, said injuries he had seen in Gaza were consistent with the use of Dime (dense inert metal explosive) bombs. "It was as if [patients] had stepped on a mine, but there was no shrapnel in the wounds," he said. A UN convention, which Israel has signed, prohibits "the use of any weapon the primary effect of which is to injure by fragments which in the human body escape detection by X-rays". This could apply to Dime bombs, but by their nature it is extremely difficult to prove they have been used.

Amnesty International last week called on Israel to give details of weapons beside phosphorus it had used in Gaza, so that medics could better treat the injuries they inflict. Donatella Rovera of Amnesty, currently on a munitions fact-finding mission to Gaza, said doctors were encountering "new and unexplained injuries, including charred and sharply severed limbs" after air strikes. The UK human rights agency also quoted Dr Subhi Skeik of Shifa hospital's surgery department as saying: "We have many cases of amputations and vascular reconstructions where patients would be expected to recover in the normal way. But to our surprise, many of them died an hour or two after operation. It is dramatic."

Dr Shaban of Shifa's burns unit said surgical colleagues had encountered bloodless amputations of limbs after attacks during the war, and that some Egyptian and Jordanian doctors with experience in Lebanon and Iraq had suggested that Dime bombs could be responsible. But both Amnesty and Human Rights Watch's weapons expert Mark Galasco, who is also in Gaza, are highly cautious about speculating on the possibility of Dime, not least because of the difficulty of finding provable traces of it.

Israel has always insisted that its weaponry – including controversial flechette darts, which have been used in Gaza before and have been found so far in two northern Gaza locations this time – is legal. There is no outright ban on Dime bombs, flechettes or even white phosphorus. It is the time and the manner in which they are used that can be illegal.

Targeting of civilians

Israel has continued to contrast what it says are its strenuous efforts to avoid civilian casualties with Hamas's undoubtedly deliberate targeting of civilians with Qassam rockets. There have, however, been several cases in which Palestinian civilians were hit while taking shelter. In other incidents, people in Gaza said they were fired on while seeking to flee to safety, in some cases waving white flags.

In the most widely publicised case, the UN says 80 members of the Samouni family were sheltering in a warehouse hit by missiles early on 5 January, killing 29. Several survivors said they had been ordered by the army to go there the previous day. Meanwhile, Khaled Abed Rabbo said a single soldier shot three of his young daughters from a tank, killing two, as they obeyed orders to flee their home on the outer edge of Jabalya. He suggested it was a deliberate act, The army is investigating, but reaffirms that "the IDF does not target civilians".

Yesterday Mr Rabbo's mother Suad, 54, who was shot in the arm and abdomen at the same time, corroborated his account. She said she, her daughter and her seven-year-old granddaughter were all carrying white flags when they were shot. She did not see the soldier who fired, but insisted there were no Palestinian fighters in the vicinity.

Humanitarian aid

While basic humanitarian supplies, including medicine, continued to flow into Gaza from Israel during the war, the UN and other agencies complained more than once that there were severe problems in distributing food and other aid within Gaza because of continuing security problems. These were compounded when a driver contracted by UNRWA was shot dead near the Erez crossing as he prepared to load food, ready for moving it south during a three-hour humanitarian pause.

There were also several complaints from the Red Cross and Israeli human rights agencies that medics and rescue services were prevented from reaching the wounded and dead. Four weak and terrified children from the Samouni family were finally found by the Red Cross, two days after the attack that killed 29 other family members.

After the ground attack started, one convoy, consisting of an ICRC truck and a Palestinian Ministry of Health truck, both carrying medical supplies for hospitals in southern Gaza, and 13 ambulances carrying intensive care patients to Egyptian hospitals, had to turn back after the ICRC driver was shot and injured near a military checkpoint in the centre of the strip.

Fuel shortages and power cuts continued to deprive about a million Gazans of electricity at any one time. Sewage and water supplies were badly hit, because pumps could not operate.