Deep uncertainty surrounds the latest events in Venezuela.

Tuesday began with a pre-dawn recorded address to the public by interim president Juan Guaidó, who stood with members of the security forces at a Caracas air base and declared that a long-anticipated barracks uprising against the regime of Nicolás Maduro had begun. Accompanying Mr. Guaidó was opposition leader Leopoldo López, apparently released from his four-year detention by defecting guards. Venezuelans responded to Mr. Guaidó’s call for street protests and were met by troops loyal to Mr. Maduro. By late afternoon, clashes were taking place, regime officials were promising a decisive “counterattack,” and there was no way to know whether “Operation Liberty,” as Mr. Guaidó dubbed this high-risk move, would succeed or be crushed – or devolve into civil war.

What is not, or should not be, ambiguous is the political and moral essence of this volatile situation. The Maduro regime has violated human rights on a massive scale, leaving hundreds of peaceful opponents dead, and it has led Venezuela into economic catastrophe. Millions of Venezuelans have fled to other countries, including hundreds of thousands to the United States. Having first been elected in 2013, Mr. Maduro forfeited democratic legitimacy in January 2016, when he purported to deprive the National Assembly of its powers because the opposition had won control the previous month. He then manipulated the political system to create a parallel puppet legislature and, on May 20, 2018, engineered his re-election through a flawed process from which both international observers and leading opposition figures were effectively barred. His inauguration as president for a new term in January, in defiance of warnings from neighboring Latin democracies, prompted Mr. Guaidó, leader of the National Assembly, to declare the presidential office vacant and himself its interim occupant, as provided in the Venezuelan Constitution – and supported by more than 50 countries, including the United States.

Therefore, whatever its ultimate outcome or, indeed, its strategic wisdom, Tuesday’s uprising is not a “coup attempt,” as the Maduro regime, echoed by too many people abroad, calls it. Rather, it is the latest in a series of legitimate and, for the most part, nonviolent efforts by Venezuelans, both civilian and military, to throw off an oppressive, toxic regime so that they can freely elect a legitimate government. Supporters of freedom and democracy should stand in solidarity with Mr. Guaidó and the many thousands of Venezuelans now bravely asserting their rights.

The Trump administration has backed Mr. Guaidó, including – appropriately – through the use of tough new economic sanctions aimed at pressuring the Maduro regime to cede power, or persuading the Venezuelan military to oust him itself. Possibly, Tuesday’s events are a sign that Mr. Trump’s policy is succeeding; or, possibly, that there is nothing left of it but desperate measures. A hopeful sign was the immediate and unequivocal backing Mr. Guaidó received from six South American nations, including Venezuela’s four largest neighbors: Colombia, Ecuador, Brazil and Peru. By working closely with these countries, and not by intervening militarily, the Trump administration may increase the chances that Mr. López’s declaration Tuesday – “It’s time to conquer freedom” – proves out.