Fresh turmoil has hit the Pentagon after Dan Driscoll, the Secretary of the Army and the most senior civilian in the US Army’s leadership, resigned following months of sharp disagreement and a personal clash with Defence Secretary Pete Hegseth.

According to the Financial Times, Driscoll submitted his resignation to President Donald Trump on Monday, effectively condemning Hegseth’s interference in the largest branch of the US armed forces. A person familiar with his thinking said Driscoll believed the Defence Secretary was causing damage that would affect an entire generation of the Army.

“He had tried in so many different ways and so many times, but it became clear that Hegseth was not willing to listen to facts, truth or reason, because of his personal antipathy,” the same source said.

Driscoll’s departure adds to a series of internal conflicts at the Pentagon, which is already grappling with a reshuffle of its senior military leadership, while the US remains locked in a protracted conflict with Iran that is straining military capacity and ammunition stockpiles.

“This is a revealing moment, and I think it shows the Pentagon is in disarray,” said Tom Wright, a senior fellow at the Brookings Institution, the Washington based think tank.

The battle over the Army’s leadership

One of the biggest flashpoints between Driscoll and Hegseth was the removal, last April, of Army Chief of Staff General Randy George.

Since the start of Trump’s second term, Hegseth has removed or forced out roughly 24 generals and admirals in a sweeping overhaul of the military leadership.

Driscoll’s resignation now leaves the Army without a permanent civilian head or a permanent chief of staff, two posts that require Senate confirmation.

The vacancy is seen as especially critical, given the US Army’s significant role in missile defence through the Patriot and THAAD systems, while thousands of American troops remain deployed for extended periods across the Middle East.

Chris Meagher, a former senior Pentagon official under the Biden administration, described Driscoll as one of the few senior civilian officials considered “relatively level-headed,” who enjoyed the trust of the troops and “did genuinely good work.”

He added that the absence of a permanent Army Secretary and chief of staff “creates a serious leadership gap, especially in wartime.”

The fight over drones and modernisation

The two men’s disagreements were not limited to who would fill the senior leadership posts. Driscoll had become a central figure in the Pentagon’s efforts to develop cheaper drones, counter drone technology and new missile defence systems.

According to a source familiar with his views, Hegseth was trying to obstruct this transformation process for personal reasons. Under Driscoll, the Army had tasked an infantry battalion with developing and integrating new drone capabilities. Hegseth, however, ultimately ordered the unit disbanded.

Driscoll was even considered a possible successor to Hegseth, should Trump decide to remove the Defence Secretary.

Unease among Republicans too

The resignation has caused concern even within the Republican Party. South Dakota Senator Mike Rounds said he was “disappointed” by Driscoll’s departure.

“Where is the leadership? We had some very good generals who are no longer there, and whom we respected,” he said.

Hegseth has temporarily installed Lieutenant General Christopher LaNeve, a close ally, as the Army’s top officer, and wants to make the appointment permanent.

However, some Republican senators, unhappy about the way General George was removed, have already signalled that confirming LaNeve’s nomination will be difficult.

A congressional source said the opposition “is not about LaNeve himself,” but about Hegseth and the lingering anger in Congress over how he handled the removal of the previous chief of staff.

Driscoll’s resignation is expected, the same source said, to create further problems for the Pentagon as it seeks approval of a $1.5 trillion budget, as well as tens of billions of dollars in additional funding for the war with Iran.

The Navy under pressure too

The turbulence is not confined to the Army. The Navy is also under significant strain, both operationally and financially. Operations stretching from the Caribbean to Iran have increased the use of warships and depleted missile stockpiles.

Navy Secretary John Phelan was removed in April, and Trump has proposed as his successor acting Navy Secretary Hung Cao, a former Navy captain.

Democratic Senator Jeanne Shaheen, a member of the Senate Armed Services Committee, aimed her criticism squarely at Hegseth. “Secretary Hegseth is the one who should have resigned, after his mishandling of military operations in the Middle East and around the world,” she said.

“It is unthinkable for Secretary Hegseth to be purging the ranks of top military officials at the very moment the US is in an ongoing conflict and security challenges are mounting,” she added.

Trump continues to back Hegseth

Despite pressure from within the Pentagon and from members of Congress, Pete Hegseth continues to enjoy Donald Trump’s public backing.

Asked about speculation that the Defence Secretary might even be weighing a 2028 White House bid, the US president praised him. “He has done a fantastic job,” Trump said. “Right now, the only thing he loves and the only thing he cares about is the military and taking care of the military.”

Democratic Senator Elissa Slotkin, meanwhile, argued that Hegseth operates with “an audience of one, Donald Trump.” “If someone disagrees with him, undermines him, or in some way makes him look weak, he gets rid of them,” she said, adding that the situation at the Pentagon was beginning to resemble “a purge without end.”

Driscoll himself, however, avoided publicly attacking Hegseth in his official resignation statement. He announced he would leave his post on Wednesday and noted that he had “had the privilege of working to modernise and accelerate the way the Army recruits, trains and equips the most lethal fighting force in the world.” He added that the progress made would not have been possible “without the support of Secretary Hegseth.”