There are no pictures of Vladimir Putin's encounter with Malcolm Turnbull at the G20 in Hangzhou, but his message on the Syrian war could not be clearer.

The Russian strongman listed the litany of Western errors in the Middle East, saying George W Bush should never have unsettled the region by deposing Iraqi dictator Saddam Hussein.

The United States and Australia were repeating the error in Syria and playing into the hands of radical Islam, he said.

"I'm fighting for the legitimate Government of Syria," Mr Putin added.

"Who are you fighting for?"

It was, Australian sources conceded, a very good question.

The exchange highlights the value of the summit season. Behind the impenetrable bureaucratise of the obligatory communiques, the leaders have very frank conversations where disputes and hopes are boiled down to their essence.

And this does not just happen in the official "sideline" meetings, but in momentary encounters on conference room floors and in corridors.

A Russian warplane drops bombs over Syria. The Kremlin argues it is fighting on behalf of the country's legitimate Government ( AFP/Russian Defence Ministry )

Turnbull's 'funk' lifted on G20 journey

In another snapshot with Mr Turnbull, Turkey's President Recep Tayyip Erdogan called on an aide to produce an iPad, and the Prime Minister was shown a map of Turkey's border with Syria.

Mr Erdogan pointed to a zone inside Syria, 90 kilometres wide and 40km deep. It was there that he proposed to set up a safe zone for refugees, policed by Turkey's military. Observers say that the other way the map could be read was that it split Kurdish forces.

The Prime Minister has had a grim time of it at home since the beginning of this year and he has been weakened by an election that reduced his majority to a single seat in Parliament.

It has been obvious that his confidence has been rocked and his public appearances have not lost the wooden edge of his campaigning.

But that funk has lifted on this journey. Released from the grind of the daily politics that he has yet to master, and liberated to focus on some of the world's larger problems there has been a clear change in Mr Turnbull's demeanour. He is smiling and engaged in public, and in private is wrestling with Australia's role in what has become a very unsettled world.

And the West's position in the world is now as weak as Mr Turnbull's is at home. Europe is in a state of constant political and economic crisis, exacerbated by the march of a million asylum seekers and Brexit.

Russia, China emboldened by sense of US in decline

Chinese marines in the South China Sea. Will the East China Sea be the new flashpoint? ( Reuters )

The changing of the guard in the United States has exposed the deep and widening internal fissures in that nation and reinforced the sense that the world's only superpower is in decline. That has emboldened Russia, which is pushing out its elbows as it seeks to regain the place it lost with the fall of the Soviet Union.

Australian officials worry that Chinese president Xi Jinping is making the same calculation as Mr Putin, fortifying islands in the South China Sea and paying little heed to protests.

One noted that the pattern of behaviour is for Beijing to push out, be met with protest, and then pause before pressing ahead again.

That is what's happening the East China Sea where, after a period of relative calm, China has recently stepped up activity around the disputed Senkaku Islands.

That has an already worried Japan in a flap. Mr Turnbull met with Japan's Shinzo Abe on Wednesday, and responding to China's assertiveness was no doubt high on the agenda.

As flashpoints go, it might be the East China Sea that is now the place to watch. There, a nationalistic China is confronting an equally determined Japan that has reinterpreted its pacifist constitution in preparation for a fight. That is a dangerous cocktail.

Everyone hopes that will not happen, that deep economic ties will make the cost of a conflict too high for all. But countries do not go to war because they want to. They do it when they believe the alternatives are worse.