Venezuela holds the world’s largest supply of crude oil, and petroleum products make up the vast majority of the country’s exports.
Production held virtually steady from 2002 – just before the national strike – to 2008, when global oil prices peaked. Figures from the Organization of the Petroleum Exporting Countries (Opec) show the country earned bout $60bn from oil that year.
But the collapse in oil prices towards the end of 2014 – a year after Mr Chávez died from cancer – decimated the country’s already-struggling oil-dependant economy.
The country hit crisis levels the following year, with GDP shrinking by almost 6% and inflation soaring.
Oil output has been declining since.
6. Many Venezuelans are leaving
Three million Venezuelans have left their home country since 2014, according to the UN.
The majority of those leaving have crossed into neighbouring Colombia, some then move on to Ecuador, Peru and Chile. Others have gone south to Brazil.
Vice-President Delcy Rodríguez has disputed the UN’s figures, saying they are inflated by “enemy countries” trying to justify a military intervention.
7. Countries are split over who to support
The US, more than a dozen Latin American countries, and Canada have already backed Mr Guaidó – leader of Venezuela’s elected National Congress – undermining President Maduro, who began a second term in office just a fortnight ago.
On Saturday, Spain, Germany, France and the UK said they would officially support Mr Guaidó if new elections were not called within eight days.
But Russia has condemned foreign support for Mr Guaidó, saying it violates international law and is a “direct path to bloodshed”. China, Mexico and Turkey also back Mr Maduro.
By Dominic Bailey, David Brown, Daniele Palumbo, Lucy Rodgers, Olesya Volkova, Sean Wilmott.