Russia is a permanent member of the UN Security Council (maintain international peace and security) and a signatory to the Geneva Conventions of 1949 (protect innocent civilians at times of war) but Putin has ignored these legal obligations.

Further, Russia has directly employed tens of thousands of mercenaries to wage war on Ukraine; is the Wagner mercenary group a legitimate military resource or a large-scale contract killer?

Ukraine war latest - live updates

The priority of any nation's rulers is defence of their lands and people. The authority to bear arms enables the military to fight and if necessary, kill their enemies, but there are strict laws that govern the use of lethal force.

The Law of Armed Conflict and the Geneva Convention of 1949 (first edition 1864) - enshrined in international law (signed by nearly 200 nations including Russia) - provide a legal framework for the conduct of war.

Although there might be sceptics - in ancient Rome Cicero stated that "laws are silent amidst the clash of arms" - these laws are legally binding, and any breaches are investigated as war crimes.

For a professional military force the study of, and adherence to, the Law of Armed Conflict is an essential foundation of military training. It underpins the authority to bear arms and provides an essential discriminator between lawful warfighting and unlawful killing.

Mercenaries, however, have no such mandate - they fight for money and personal gain, with no regard for consequences.

Read more:
What is the Wagner Group of 'secret' Russian mercenaries?
Explosions in Kyiv as Russia steps up attacks and targets power
35 countries 'back Olympic ban' on Russian and Belarusian

They are not trained in the Law of Armed Conflict or understand their obligations under the Geneva Convention; their very existence on the battlefield demonstrates President Putin's complete disregard for Russia's international legal obligations.

In the civilised world, even warfare is conducted within a legal framework to protect innocent civilians and provide basic protections for the wounded and prisoners.

Click to subscribe to Ukraine War Diaries wherever you get your podcasts

In commissioning a mercenary group to fight Russia's war in Ukraine, Putin has abandoned any sense of humanity, has ridden roughshod over the legally agreed Law of Armed Conflict, and is directly responsible for the growing list of war crimes for which he will - eventually - be called to account.

Russia was once a superpower state, respected and with global standing; however, in violating the basic principles of the Geneva Convention, instead of achieving greatness, Putin's Russia has become a pariah state, and Putin is solely responsible.