The head of the Pentagon's Southern Command is to step down at the end of the year, two years ahead of schedule, amid mounting tensions over the Trump administration's military operations in the Caribbean targeting alleged Venezuelan drug traffickers.

Admiral Alvin Holsey, who oversees all US military operations in Central and South America, announced on October 16 he would retire on December 12, less than a year into what is typically a three-year posting. The abrupt departure comes as the Pentagon has deployed roughly 10,000 troops to the region in what it describes as a counter-narcotics mission.

Defence Secretary Pete Hegseth, who has controversially rebranded his position as "Secretary of War," made no mention of policy disagreements in his public statement, saying: "On behalf of the Department of War, we extend our deepest gratitude to Admiral Alvin Holsey for his more than 37 years of distinguished service to our nation as he plans to retire at year's end."

However, two US officials told the New York Times that Admiral Holsey had raised concerns about the mission and attacks on suspected drug vessels, speaking on condition of anonymity to discuss personnel matters.

The timing of the admiral's departure has alarmed Democratic lawmakers, particularly given the rapid US military build-up in the Caribbean and escalating rhetoric towards Venezuela's President, Nicolás Maduro, who Washington accuses of heading the alleged narcotrafficking group “Cartel de Los Soles.”

Senator Jack Reed, the ranking Democrat on the Senate Armed Services Committee, said the resignation sent "an alarming signal of instability within the chain of command".

"Admiral Holsey's resignation only deepens my concern that this administration is ignoring the hard-earned lessons of previous US military campaigns and the advice of our most experienced warfighters," Reed said.

Since early September, US Special Operations forces have struck at least six boats off the Venezuelan coast, killing at least 29 people. The White House has justified the attacks by claiming the vessels were transporting drugs, though American officials have privately acknowledged the main objective is forcing Maduro from power.

The operations have sparked concern amongst legal experts, who dispute the administration's claim that it can lawfully kill suspected drug traffickers as if they were enemy combatants, rather than arresting them for prosecution. Congress has not authorised any armed conflict, whilst under international law, targeting individuals based solely on their status requires them to be part of an organised armed group engaged in hostilities.

Representative Adam Smith, the senior Democrat on the House Armed Services Committee, said Admiral Holsey's early departure was unprecedented. "Prior to Trump, I can't think of a combatant commander who left his or her post early, ever," he said, as quoted by the NYT.

The departure adds to a growing list of senior military officers who have left their posts this year under Hegseth's controversial tenure, many of them black or women. The defence secretary has fired or pushed out more than a dozen military leaders, including General Charles Q Brown Jr, the chairman of the Joint Chiefs of Staff, and Admiral Lisa Franchetti, the first woman to command the Navy.

Admiral Holsey, one of only two Black four-star officers leading a US combatant command, gave no explanation for his decision in a message posted on Southern Command's social media account. "The SOUTHCOM team has made lasting contributions to the defence of the nation and will continue to do so," he said.

The current US force posture in the Caribbean includes eight Navy warships, a nuclear submarine, and approximately 2,200 Marines on amphibious assault ships, with the majority of personnel based in Puerto Rico. The Pentagon announced last week it would create a new counter-narcotics joint task force, though operational command has controversially been assigned to II Marine Expeditionary Force rather than Southern Command.

The Trump administration has justified the attacks as national self-defence amid high US overdose deaths, though the surge has been driven primarily by fentanyl entering from Mexico rather than cocaine from South America.

News of Admiral Holsey's departure emerged a day after reports that President Trump had secretly authorised CIA covert operations in Venezuela aimed at unseating Maduro. Trump confirmed the authorisation on October 15 and said the US was considering strikes on Venezuelan territory.

Senator Tim Kaine is preparing to force a vote on a war powers resolution in the coming weeks to prevent Trump from using military force in Venezuela without congressional approval, The Hill reported. A similar measure failed last week by 48 votes to 51, though it gained support from two Republican senators.

It remains unclear who will replace Holsey at Southern Command.