Dan Caldwell is not a name many Americans know. But inside Washington’s national security circles, he was a man on the rise. That is, until he was escorted from the Pentagon on Tuesday and placed on administrative leave. Caldwell is one of three Defense Department officials who have been ensnared in a leak probe that began last month.
Caldwell was a senior adviser to Defense Secretary Pete Hegseth, a close personal friend who he first met when both worked for the conservative nonprofit Concerned Veterans of America in the early 2010s. Before his boss was confirmed by the Senate, he headed a “landing team” to place mid-level officials inside the vast defense bureaucracy. He was one of the leaders of the “restrainer” faction inside the Trump administration, a network of policy wonks that have sought to end many of America’s overseas commitments and interventions. Caldwell was so trusted by Hegseth that he served as his proxy on the Signal group chat discussions over the plans to bomb Houthi rebels in Yemen.
And yet on Tuesday Caldwell was marched out of the Pentagon. The question is why?
The story appears to start with a March 20, 2025 story from The New York Times that first reported that Elon Musk was scheduled to receive a Pentagon briefing on military plans for war with China. That story prompted Hegseth’s chief of staff, Joe Kasper, to launch an investigation into leaks of national security information.
That memo, however, referred to “recent unauthorized disclosures of national security information involving sensitive communications,” meaning there was more than one leak. Once a leak investigation starts, it may turn up other leaks the investigators were not even trying to initially find.
One possible leak in the crosshairs of the investigation is a New York Times story from April 4 on how the military was burning through its munitions in the multiple strikes against Houthi targets in Yemen, with little success. As the Signal chats published by The Atlantic showed, one of the administration’s leading restrainers, Vice President J.D. Vance, opposed that operation. Hegseth, however, was supportive.
The Pentagon’s computer system logs every button pushed on a keyboard from the lowest level administrative assistant to a powerful senior adviser to the secretary of defense. One Republican operative who works closely on military affairs quipped, “Did these Metterniches not realize that every keystroke in that building is monitored?”
Along with Caldwell, the investigation has also led to the suspension of Colin Carroll, the chief of staff to deputy defense secretary Steve Feinberg, and Darin Selnick, who had just been promoted to Hegseth’s deputy chief of staff. One Trump administration official told The Free Press he expected more officials to be caught up in the leak probe this week.
Caldwell’s exit from the Pentagon is a minor victory for the more hawkish wing of the Trump coalition. Caldwell was a lobbyist between 2017 and 2020 for the Charles Koch–funded Americans for Prosperity. He was also a public policy adviser at Defense Priorities, a new Washington think tank that advocates against American interventionism. That said, the leak investigation does not appear to be cover for an ideological purge. Carroll is not part of this restrainer coalition inside the Trump administration.
If Caldwell, or the other officials who have been placed on administrative leave, provided top-secret information to someone not authorized to receive it, they could face felony prosecutions from the Justice Department.
Whatever happens next, the leaks have not stopped. On Wednesday evening, The New York Times published a juicy and detailed account of how the restrainers won an internal Trump administration debate and persuaded the president to wave off a potential Israeli strike on Iran’s nuclear facilities. It is unclear whether the officials, or official, responsible for that leak have yet been fired.
