WASHINGTON — When Defense Secretary Pete Hegseth steps into his office on the Pentagon's third floor E Ring on Monday morning, he will have a daunting array of issues to tackle — from global conflicts and border security to administrative tasks.

At the top of his list is addressing President Donald Trump's priority to strengthen the U.S. military presence along the southern border and reviewing whether active-duty forces should be used for law enforcement — something done rarely.

Dozens of other issues will compete for his attention, including developing the Pentagon's massive budget, decisions about aid to Ukraine, support for the ceasefire in Gaza, troop deployments in the Middle East. Not to mention Trump directives to rid the federal government of diversity programs and personnel as well as moves to cut waste and remove any lingering Biden administration backers.

In a message to the force shortly after he was sworn in Saturday, Hegseth cited the challenges he sees ahead. Some are ones his predecessors also faced, such as reorienting the military from decades of a Mideast focus and better deterring China. Continued conflict in the region, including the October 2023 attack on Israel by Hamas, has made that shift impossible to execute.

Hegseth also told service members about other priorities, including strengthening the defense industrial base and getting the Pentagon to pass an audit, while ensuring that the U.S. remains ''the strongest and most lethal force in the world."

Already, support staff have been meeting with military leaders, including Gen. CQ Brown Jr., chairman of the Joint Chiefs of Staff. But Hegseth will get to experience what many describe as ''drinking from a firehose'' as he works to quickly get up to speed on what his 2.1 million service members and 780,000 civilians in the department are doing. Among them are tens of thousands serving overseas, including in combat zones.

Then there are the cultural issues that Hegseth railed on as a media personality that did not make it into Hegseth's message to the military. Many expect they will surface in the coming days.

Here are some key issues that Hegseth, who was confirmed in a tiebreaking vote Friday by Vice President JD Vance, will face right away:

Border deployments

In trying to meet Trump's demand of securing the border, Hegseth will face a barrage of information about what troops are available, what assistance the Border Patrol needs and where, as well as how to house, feed and transport the troops and border personnel and how to ensure none of this affects other national security requirements.

One of his first big decisions is whether he will recommend that active-duty troops deployed to the border get involved in law enforcement, a move that military leaders in recent years have pushed to avoid.

Active-duty forces are prohibited from doing law enforcement duties on U.S. soil under the Posse Comitatus Act. Trump has signed an executive order directing that his defense and homeland security secretaries report back within 90 days on whether they think he should invoke the 1807 law called the Insurrection Act, which allows troops to be used for civilian law enforcement on U.S. soil during emergencies.

During previous deployments, troops have been used for transportation, intelligence, logistics, wall-building and other support tasks, freeing up the Border Patrol to interact with migrants and conduct the law enforcement duties.

Transgender troops

In his first executive order, Trump again stripped protections for transgender troops that Democratic President Joe Biden had restored after Trump banned those members from serving during his first term in office.

The ban previously faced legal challenges, and lawyers who represented transgender forces last time are readying to take it up in the courts again. While Trump has not announced a ban, his decision to revoke protections is seen as a first step toward that.

It is unclear how many troops would be affected. The Defense Department has no exact figure on the number of transgender troops serving because not every transgender person is in the same state of medical transition and not every transgender person identifies as such in military paperwork.

The department has referred queries on how many transgender troops there are to the services; the services have said they have no way to track.

The budget and Ukraine

Hegseth will have to become familiar with the complicated construction of the Pentagon budget, which right now is about $850 billion. Trump ran on a vow to make the U.S. military more lethal — something Hegseth has echoed. But they also have spoken extensively about cutting waste.

So Hegseth's imprint on the budget will be studied to determine how that's being done.

Woven into those discussions will be security assistance to Ukraine. The State Department has ordered a freeze on new funding for almost all U.S. foreign aid, and there was no indication of a waiver for military assistance for Ukraine like there was for Israel and Egypt.

The Biden administration provided Kyiv with more than $66 billion in military aid and weapons during the war with Russia. It had left unspent about $3.85 billion in congressionally authorized funding to send more weapons to Ukraine from existing U.S. stockpiles — a sum that is not affected by the foreign aid freeze. But it is now up to Hegseth and Trump to decide whether or not to spend it, and Trump hasn't said what he will do on Ukraine aid.

Diversity, equity and inclusion rollbacks

Hegseth will take over the Pentagon's push to implement Trump's executive order to get rid of DEI programs, coming as military officers fret over whether they will be fired for being ''woke," as Hegseth has pledged to do.

During his Senate hearing, Hegseth affirmed his commitment to focus on lethality and to eliminate wokeness, arguing that DEI policies ''divide'' troops and do not prioritize ''meritocracy.''

Officials said the Defense Department doesn't have any full-time workers assigned to DEI so they don't expect to have to fire people, as other federal agencies have.

But senior leaders have been poring over their websites to delete pages that mention diversity. Lacking clear guidance, staffers were pulling websites down in often inconsistent ways. The Army, for example, temporarily removed its sexual assault guidelines before they later came back online.

Hegseth also has railed against women in combat in his books and on podcasts and said standards were lowered for them, which is not true. He has since toned down his criticism after substantial pushback from lawmakers.

He most recently told senators that he's not aware that Trump wants to roll back the decision to allow women to serve in all combat jobs. Instead, he has talked about doing a review of standards.

Reproductive care

After the Supreme Court in 2022 ended constitutional protections for abortion that were set out in Roe v. Wade, then-Defense Secretary Lloyd Austin came out with a policy that would allow service members to take leave and be reimbursed for travel expenses to obtain reproductive care — including abortions and in-vitro fertilization — if the military base they were assigned to was in a state that had banned that care.

It's not clear whether Hegseth will seek to further revise that policy to remove the reimbursement provisions. It has been only scarcely used, and the department does not break down what the travel was for due to medical privacy laws.