As Vladimir Putin’s war enters its third year, it is time to count the bodies. Ukraine admits to 31,000 deaths suffered by its troops. The actual toll is probably much higher, not to mention all the serious injuries. Tens of thousands of its civilians have lost their lives, including hundreds of children, while 21,000 young people have been kidnapped and taken by force to Russia.

Damage to infrastructure and housing and the environment has been huge. Russia has not dared to admit to the number of its military casualties, estimated at more than four times that of Ukraine. It is thought that by the end of this year, half a million people will be dead or disfigured.

What does international law say about all this?

Hear no evil? Russian President Vladimir Putin Credit: Sputnik, Kremlin Pool via AP

It says, very clearly, that Putin is guilty of invading another country for no good reason and, as one of the founders of international law, Emmerich de Vattel, said centuries ago, the Russian leader bears legal responsibility for “all the evils, all the horrors of war; all the effusion of blood, the desolation of families, the rapine, the ravages are his works and his crimes”.

Vattel, of course, could have had no conception of the further horror of nuclear war that Putin threatened only on Thursday against any NATO country that sent military forces to Ukraine’s defence. Sabre-rattling or not, the very threat of such attack constitutes, in my judgment, a crime against humanity.

Modern law makes a leader guilty if the United Nations Charter is breached by his decision to invade another member state with a force of the “character, gravity and scale” that makes the breach “manifest”. This definition of aggression fits Putin and his war like a glove.

The only defence Putin can offer – which he has already signalled to the UN Secretary General and to the obsequious American interviewer Tucker Carlson – is self-defence under article 51 of the charter. He claims his entitlement to attack and kill Ukrainians because the country might have joined NATO, and NATO might have attacked Russia. This is called “pre-emptive self-defence” – invented by George Bush’s lawyers in 2003 as an excuse for attacking Saddam Hussein in case he acquired nuclear weapons that he might one day use against the US.

It is ironic that Putin should rely on a doctrine that Russia, as well as all other countries except Israel, regarded as a perversion of international law, at a unipolar moment when the US could do and say pretty much what it liked. The United Kingdom and Australia did not endorse it but relied instead on a highly doubtful theory about the “revival” of an old Security Council resolution about Saddam’s invasion of Kuwait. America itself has since resiled from claiming a right to pre-emptive self-defence, which would be a blank cheque for any powerful country to invade another on mere speculation about its future hostility.