WASHINGTON — For the past month, the Navy cruiser San Jacinto had sailed off the West African island nation of Cape Verde on a secret mission aimed at helping deal a major blow to President Nicolás Maduro of Venezuela, an avowed adversary of the Trump administration.

The mission was set in motion in early June, when Alex Saab, a Colombian businessman who is widely believed to be the architect of the economic deals that are keeping the Maduro government afloat, was arrested in Cape Verde when his private plane stopped to refuel en route to Iran from Venezuela. The United States sought his extradition under U.S. money laundering charges, and judicial proceedings began.

"Saab is critically important to Maduro because he has been the Maduro family's frontman for years," said Moises Rendon, a Venezuela specialist at the Center for Strategic and International Studies in Washington. "Saab has access to privileged information to Maduro's corruption schemes in and outside Venezuela."

The subsequent stealthy arrival of the U.S. warship coincided with President Donald Trump's firing of Defense Secretary Mark Esper in early November. For months, Esper had fended off pleas from the State and Justice departments to deploy a Navy vessel to Cape Verde to deter Venezuela and Iran from plotting to spirit Saab away from the island. Esper said sending in the Navy was a misuse of U.S. military might. A Coast Guard cutter was dispatched in August instead.

With Esper out of the way, however, his replacement, Acting Defense Secretary Christopher Miller, a former White House counterterrorism aide, quickly approved the San Jacinto's deployment from Norfolk, Va.

In the waning days of Trump's term, the tale of the San Jacinto and its unlikely monthlong mission illustrates what critics say is the administration's capricious use of the armed forces — deploying troops to the southwestern border one day, yanking other troops abruptly from northeast Syria the next.

It is also the latest effect of Trump's purge of the Pentagon's top leadership and his installment of largely hard-line loyalists. With Esper gone, Miller has ordered deeper troop cuts in Afghanistan, Iraq and Somalia; ousted the policy official overseeing the military's efforts to combat the Islamic State; and considered pulling back military support for the CIA, including its drone fleet.

The showdown over Saab is the latest twist in the tense relationship between the United States and Venezuela. In 2017, Trump said he would not rule out a "military option" to quell the chaos in Venezuela. In 2018, the Trump administration held secret meetings with rebellious military officers from Venezuela to discuss their plans to overthrow Maduro.

And in August, the United States seized more than 1.1 million barrels of Iranian fuel that was headed to Venezuela in a high-seas handover that blocked two diplomatic adversaries from evading U.S. economic sanctions.

So administration aides were elated when officials in Cape Verde arrested Saab on his fuel stop, responding to a wanted alert from Interpol known as a red notice, which had been in effect because of the U.S. money laundering charges.

Maduro's foreign minister, Jorge Arreaza, condemned the detention, calling it an act "violating international norms and law."

If Saab cooperates with U.S. officials, he could help untangle Maduro's economic web of support and assist authorities in bringing charges against other allies of the Venezuelan government.

Washington has accused Saab of "profiting from starvation" through his involvement in a scheme in which he and others are suspected of making off with large sums of government funds meant to feed Venezuela's hungry population. U.S. officials have said that this was part of a larger scheme in which Maduro's allies bought less or lower-quality food than requested in contracts and redistributed extra money to loyalists.

Saab is one of several Maduro-linked officials and businessmen indicted by the U.S. government in recent years, including Maduro himself. The U.S. and more than 50 other nations view Maduro's government as illegitimate and recognize a political rival, Juan Guaidó, as the country's interim president.