Yet despite the carnage and reports of tanks in the middle of Rafah, Mr Biden’s people are dancing on pins. It was now all about scale, not the actuality. “We have not seen them go in with large units and large numbers of troops in columns and formations in some sort of coordinated manoeuvre against multiple targets on the ground,” said John Kirby, Mr Biden’s national security spokesman on Tuesday night.

He added: “We have not seen them smash into Rafah.”

Some say the strike which sparked the inferno in Rafah was no more than an accident – a “tragic mishap” as the Israeli premier Benjamin Netanyahu put it – but that’s not the whole truth of it. To understand why you only need to look at the laws of war and President Obama’s first military decision of consequence – the killing of Osama bin Laden on May 2, 2011.

Why didn’t Mr Obama drop a big bomb on the al-Qaeda leader once he had worked out where he was hiding, or even a smaller smart bomb? Why did he risk the lives of two dozen brave and professional US Navy SEALS acting thousands of miles away from home instead?

The answer is simple. Bombing the compound was deemed illegal. There was at least one other property within the vicinity of the blast radius and it was calculated that up to a dozen civilians would be killed in addition to those in the compound. US military lawyers understood it would breach the rules of proportionality in conflict. And remember, this was in a case involving Osama bin Laden – perhaps the highest value terrorist target that ever existed.

Now consider the calculation of proportionality in the Rafah strike – something Israeli military lawyers and commanders would have had to have done and documented ahead of time if they don’t want to end up in a dock in the Hague.

According to the IDF itself, their targets were two men the Israelis had themselves deported to Gaza. One was said to be Hamas’ “West Bank staff commander”, the other a “senior staff officer”. 

They had indeed been convicted of terrorist offences in the past but that was in the early 2000s, and before they were released by the Israel authorities. The strategic military gain in killing them seems limited at best.

Now take the other side of the proportionality equation.

The men were just a 100 metres from a designated “safe area”, dense with hundreds of cloth tents, fuel supplies and thousands of women and children. Israel dropped two GBU-39 smart bombs with 17kg charges into that environment in the dead of night.

Video shot by witnesses after the attack shows an inferno sparked by some sort of secondary explosion.

“People scream as they pull charred bodies from rubble while flames rage behind them. One man holds up the body of a headless child,” reported the New York Times.

Of course there is a significant difference between Ghouta and Rafah so far as the US is concerned.

Mr Obama simply failed to enforce his red line; Mr Biden, in contrast, can be seen as an active participant – an accessory.

Those GBU-39 munitions may be smaller than the 2,000-pound dumb bombs that killed some 15,000 Gazans in the homes in the first three weeks of the war but they are also American made.