The meeting comes against a backdrop of increasing international tension:

• Russia is again at the center of possible aggression against a neighbor, this time Ukraine, which recently declared martial law in response to an escalating conflict between the two countries that most recently involved Russian ships firing at Ukrainian ships and then seizing the ships and crews. U.S. President Donald Trump canceled a planned meeting with Russian President Vladimir Putin in response to the latest events.
• Saudi Arabia is very much in the public eye after the disappearance and suspected murder of a journalist who had long been critical of the Saudi government.
• Saudi Arabia has also become heavily involved in a civil war in neighboring Yemen.
• China and the U.S. are in an on-again-off-again war of words and tariffs in what many think is the early stages of a trade war. The country's two leaders are scheduled to meet face-to-face during the summit.

The countries that make up the G-20 (or Group of Twenty) are these:

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• Argentina
• Australia
• Brazil
• Canada
• China
• France
• Germany
• India
• Indonesia
• Italy
• Japan
• Mexico
• Russia
• Saudi Arabia
• South Africa
• South Korea
• Turkey
• United Kingdom
• United States.

Argentina has declared Friday, the first day of the summit, a national holiday and urged many residents of Buenos Aires to leave the city in order to avoid what will be a big security presence. Also planned for Friday are what has become a G-20 tradition–protests.

The G-20 was formed in 1999, in response to a large financial crisis in Asia. The group was originally a meeting of finance ministers. The G-20 Summit is a relatively new meeting. It began with a meeting in November 2008 in Washington, D.C., and then became twice-a-year summits for 2009 and 2010 (London, Pittsburgh, Pa., U.S.; Toronto, Seoul) but is (as of 2011) an annual event.