It will be lawmakers' first chance to ask Hegseth about a myriad of other controversial spending by the Pentagon, including plans to spend hundreds of millions of dollars on security upgrades to turn a Qatari jet into Air Force One and to pour as much as $45 million into a parade recently added to the Army's 250th birthday bash, which happens to coincide with Trump's birthday on Saturday.
Lawmakers may quiz Hegseth on the latest searing images coming out of the immigration raid protests in Los Angeles. Hegseth has deployed about 700 active-duty Marines to assist more than 4,100 National Guard troops in protecting federal buildings and personnel. But there are questions about what the troops will have to do and how much it will all cost.
Under the Posse Comitatus Act, troops are prohibited from policing U.S. citizens on American soil. Invoking the Insurrection Act, which allows troops to do that, is incredibly rare, and it's not clear if Trump plans to do it.
The commandant of the Marine Corps, Gen. Eric Smith, will be on Capitol Hill testifying at a separate budget hearing at the same time as Hegseth and is likely to face similar questions.
What Hegseth has focused on so far
Hegseth has spent vast amounts of time during his first five months in office promoting the social changes he's making at the Pentagon. He's been far less visible in the administration's more critical international security crises and negotiations involving Russia, Ukraine, Israel, Gaza and Iran.
Most recently, Hegseth directed the renaming of a Navy ship that had honored Harvey Milk, a slain gay rights activist who served as a sailor during the Korean War. His spokesman, Sean Parnell, said the renaming was needed to ensure "the names attached to all DOD installations and assets are reflective of the commander-in-chief's priorities, our nation's history, and the warrior ethos."
Hegseth has posted numerous videos of his morning workouts with troops or of himself signing directives to purge diversity and equity programs and online content from the military. He has boasted of removing transgender service members from the force and firing so-called woke generals, many of whom were women.
He was on the international stage about a week ago, addressing an annual national security conference in Asia about threats from China. But a trip to NATO headquarters last week was quick and quiet, and he deliberately skipped a gathering of about 50 allies and partners where they discussed ongoing support for Ukraine.
His use of the Signal messaging app
Hegseth's hearing Tuesday before the House Appropriations Defense Subcommittee will be his first public appearance on Capitol Hill since he squeaked through his Senate confirmation with a tie-breaking vote. It was the closest vote of any Cabinet member.
While he has talked a lot about making the military more lethal, it was his use of the unclassified, unsecured Signal messaging app that quickly caught public attention.
Set up by then-national security adviser Mike Waltz, a group chat included Hegseth and other senior administration leaders and was used to share information about upcoming military strikes in Yemen.
The chat became a public embarrassment because the editor-in-chief of The Atlantic, Jeffrey Goldberg, was inadvertently added to it. Waltz took responsibility for the gaffe, but Hegseth was roundly criticized for sharing details about the military strikes in this chat and in another one that included his wife and brother.
Multiple investigations are looking into his use of Signal. The Defense Department's acting inspector general has been looking into the initial chat at the request of the Republican and Democratic leaders of the Senate Armed Services Committee. The Pentagon's watchdog also is reviewing whether any of Hegseth's aides were asked to delete any Signal messages.
Controversial Pentagon spending
While any number of those issues could come up at the House Armed Services Committee hearing Thursday, money issues are more likely to be the focus of the hearings Tuesday in the House and Wednesday before the Senate Appropriations Defense Subcommittee.
Already defense leaders have been grilled in other hearings on the plans to retrofit the Qatari jet and the costs of the military parade. Trump has long wanted a parade, and Army leaders defended it as a good way to attract new recruits.
Other questions may involve the costs of expanding the use of military forces to secure the southern border, the plans for the Golden Dome missile defense program, and how the department intends to fund modernization programs for drones and other critical weapons systems.