St Petersburg - The threat of missiles over the Mediterranean is weighing on world leaders meeting on the shores of the Baltic - and eclipsing economic battles that usually dominate when the Group of 20 leading world economies convenes.
Men at the forefront of the geopolitical standoff over Syria's civil war will be in the same room for meetings on Thursday and Friday - President Barack Obama, Russian President Vladimir Putin, French President Francois Hollande, UN Secretary-General Ban Ki-moon, Turkish Prime Minister Recep Tayyip Erdogan, and Saudi Prince Saun Al Faisal al Saud, among others.
The world's unemployed and impoverished may get short shrift at this summit, though activist groups are pleading with leaders to join forces to tackle corruption and tax-avoiding corporations.
The leaders represent two-thirds of the world's population, 85% of its GDP and its leading armies.
Among the topics under discussion will be:
Western bombs are unlikely to fall on Syrian government targets during this gathering. The US and French presidents are readying possible military strikes over what they say was a chemical weapons attack by Syrian President Bashar Assad's army, but both are waiting for the US Congress to weigh in first.
In the meantime, Obama and Hollande are likely to come under pressure and criticism from opponents of intervention. The UN's Ban will press for diplomatic action, amid resistance from Russia and China to any U.N.-mandated military moves.
Putin, on his own turf and looking strong in the face of Western hesitancy to tangle militarily with the Russia-backed Assad, said earlier this week that one-sided action would be rash.
The goal of some leaders at this G-20 is to get Google and other major cross-border companies to pay more taxes and stop using loopholes and tax havens.
Laudable to the general public, it's complicated both practically and politically.
>>US Federal Reserve:
The developing economies, whose vigorous growth helped the world economy survive the financial market meltdown five years ago, are now starting to falter. And they're placing part of the blame on the US Federal Reserve's expected moves to wind down stimulus measures.
With Russia set to host the Winter Olympics in Sochi in five months, this summit is the place for other leaders to pressure Putin to open up his country and himself to criticism, opposition and public debate.
Activists want pressure against Russia's gay propaganda law, a law banning adoptions by Americans, and legal cases targeting Putin opponents. The Russian leader, for his part, wants global recognition, and revenue, from these games.