Trump and his top aides have offered shifting explanations about taking action against Venezuela since the president’s military buildup in Latin America began earlier this year.

Initially, Trump defended his military operations near Venezuela as keeping drugs out of the U.S., although experts say the cocaine that passes through Venezuela winds up mostly in Europe while fentanyl is sourced from China.

Trump also accused Maduro of emptying Venezuela’s prisons and “mental institutions” into the U.S., although there’s no evidence of these claims.

According to the nonpartisan Migration Policy Institute, hundreds of thousands of Venezuelans have settled in the U.S. in recent years due to economic and political stability in their home country.

By mid-December, Trump accused Maduro of “stealing” U.S. oil and land. Trump appeared to be alluding to work done in the 1970s in Venezuela by Western oil companies before the government there opted to nationalize its reserves, eventually forcing out American companies.

In a Dec. 17 social media post — around the same time sources say Trump was making a decision to greenlight the Jan. 3 military operation — Trump said the U.S. military threat to Venezuela will “only get bigger, and the shock to them will be like nothing they have ever seen before — Until such time as they return to the United States of America all of the Oil, Land, and other Assets that they previously stole from us.”

Two days later at a press conference, Secretary of State Marco Rubio offered a more general explanation than access to oil reserves, calling Maduro’s presidency “intolerable” because it was cooperating with “terrorist and criminal elements” instead of the Trump administration.

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-ABC News’ Anne Flaherty