Accusations of war crimes have rung loud in recent months, even reaching among the most powerful people in the world.
The International Criminal Court has issued a warrant for the arrest of Russian President Vladimir Putin over the invasion of Ukraine, obliging him to miss a summit in South Africa.
And more recently, a United Nations Commission of Inquiry said it had been "collecting and preserving evidence of war crimes committed by all sides" since the latest round of violence between Israel and Hamas started last week.
But in the context of a war, defined by mass death and violence, what can be considered a crime?
What is a war crime?
The concept of improper military conduct in times of war dates back centuries - the medieval European code of chivalry being one such example.
But international "laws of war" were only developed and adopted - at least in theory - in the 19th and 20th centuries.
According to the United Nations a war crime, first and foremost, can only be committed in the context of armed conflict, whether international or domestic.
There is no single document that codifies what the UN considers to be war crimes, but they can be found throughout the Hague and Geneva conventions and related add-ons.
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What kinds of war crimes are there?
A war crime most typically involves the intentional targeting of civilians or the murder of prisoners of war.
Torture (including biological experiments), sexual assault, wilful killing, hostage-taking, unlawful deportation and targeted destruction of non-military targets are all considered breaches of international law.
Other war crimes include depriving prisoners of war of their rights and fair trial, or even making use of another country's military insignia or UN emblems - for example, to carry out an ambush.
Declaring "no quarter" - ie, that no prisoners will be taken - is also a war crime.
Certain weapons are also outlawed, from white phosphorous gas to anti-personnel mines.
Depriving civilian populations of essentials such as aid and medical supplies are also included.
Many of these also count as crimes against humanity - but that term applies to such breaches of international law outside the context of a military conflict.
Likewise, genocide, another crime the ICC had broad jurisdiction over, can take place both within and without a wartime context.
How are war crimes prosecuted?
The ICC, as noted above, can issue arrest warrants for people accused of war crimes.
However, it can only prosecute those who are brought before it by member states, as it lacks a police force.
This is why its warrant for Putin has little effect inside Russia, which in any case is not a member state.
However, if he had travelled to South Africa - which is a member state - authorities there would have been obliged to arrest him.
In short, in most cases, for war criminals to be punished they first have to lose a war.
Additionally, the court does not investigate or prosecute every allegation of war crimes around the globe. Most states have military courts or their own statutes for prosecuting war crimes.
Former Iraqi dictator Saddam Hussein, for example, was sentenced to death in 2006 by an Iraqi court for the murder of 148 Shiite Muslims in Dujail.
Before the establishment of the ICC, the United Nations could convene ad-hoc tribunals to investigate particular subjects, such as the 1994 Rwandan genocide.
Nazi war criminals were convicted by the International Military Tribunal, formed by the Allies after World War II.
The ICC does not hold global jurisdiction, with non-member states including the US, Russia, and China. Australia, however, is a signatory.
How are war criminals punished?
If somebody is brought before the ICC and convicted of war crimes, they have the right to appeal.
But if that is lost, the court will impose a jail sentence that can extend to 30 years in prison - though it also has the option to declare a life sentence.
The person sentenced will then be imprisoned in a country that has agreed to enforce the sentence.
The ICC, established in 2002, has only handed down a 30-year sentence once, to Congolese warlord Bosco Ntaganda in 2019, for crimes against humanity that included the recruitment of child soldiers.
