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The U.S. government ordered all non-emergency government workers out of Venezuela on Thursday, a day after its long-simmering tensions with the government of Venezuelan President Nicolás Maduro erupted into a crisis when President Donald Trump recognized the country's opposition leader as interim president.

Embassy security in Caracas has been bolstered, and the U.S. has re-positioned assets in the region and begun the voluntary departure of dependents of American diplomats in Venezuela, according to a senior administration official.

The State Department in recent days has been running contingency plans for potential evacuations from Venezuela and how the U.S. would respond if Maduro were to target protesters or the American embassy, a congressional official said. In the event the U.S. military needed to respond, the U.S. Southern Command could stage out of Colombia, the official said.

Other countries, including Canada, Germany and Haiti, also threw their support to Juan Guaidó, head of the opposition.

How did Trump's Venezuela move come to be?

A couple of months ago, U.S. officials began to look at ways to increase pressure on Maduro, according to the senior Trump administration official.

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About a month ago, the Venezuelan opposition began talking to National Security Council officials and those at the embassy in Caracas, the official said. The idea of invoking a particular article in the Venezuelan Constitution that would trigger the ousting of Maduro grew from those discussions, the official said. The official said the Trump administration then began to explore U.S. recognition of the new president once that article was invoked. Security of State Mike Pompeo and National Security Adviser John Bolton were for it, according to the official.

Members of the opposition told U.S. officials they needed international support to shift the political dynamic in Venezuela, the senior administration official said.

On Tuesday, Pompeo, Bolton, Commerce Secretary Wilbur Ross, Treasury Secretary Steve Mnuchin and National Economic Council Director Larry Kudlow met to discuss the options, the official said.

They then met with Trump to discuss recognition, the senior administration official said. After Trump made the decision, Vice President Mike Pence called Guaido Tuesday evening and told him: if on the following day the National Assembly invoked three article that would make him president, Trump would back him.

The policy rollout was surprisingly well-planned, according to a congressional official. The official said the White House started notifying congressional offices around 9 a.m. Wednesday that Guaidó planned to declare himself the acting leader and that the U.S. would be the first country to recognize him.

The White House had its statement prepared, portions of which were read to congressional officials, emphasizing a part about the importance of Western countries following the U.S. in recognition, the congressional official said.

This allowed lawmakers inclined to support the administration's move a chance to prepare statements in advance that were then quickly rolled out in the minutes and hours after Trump’s announcement, the congressional official said.

The senior administration official said the most significant development in the first 24 hours after Trump recognized Guaido was that Venezuela’s military has not made any moves. The official also suggested Maduro may be uncertain about his power over the military because he hadn’t ordered it to squash the protests.

The official said the U.S. believes the rank-and-file military is most likely with the opposition.

The U.S. is still figuring out ways to disconnect Maduro from the country's government money, the senior administration official said.

On oil, one option under consideration is rerouting the money from companies, like PDVSA, to Guaidó, possibly putting it in a holding place. Administration officials have been talking to businesses in Venezuela, namely Chevron and Cisco. Mnuchin and Ross have been calling financial institutions.

On Thursday, the State Department served notice to the Federal Reserve that Guaidó is the agent for access to Venezuelan assets in U.S. banks.

“We're focused on making sure that having supported the constitutional effort of the National Assembly that now we’ll provide the backup for them to succeed,” the senior administration official said.