Still officially the Army secretary, Acting Defense Secretary Mark Esper finished out his first day on the job with a memo to the Defense Department on Monday.

At the top of his list are lethality, a buzzword carried on from his predecessors, as well as building alliances and improving the department’s efficiency, according to the letter.

“Since rejoining the Department nearly two years ago as the Secretary of the Army, my confidence in the incredible skill, professionalism, and commitment of our military and civilian workforce has grown even stronger,” Esper wrote.

The retired lieutenant colonel and former Raytheon executive’s promotion was announced last week, after Acting Defense Secretary Patrick Shanahan withdrew himself from consideration. The confirmed deputy secretary of defense, Shanahan had been filling in since early this year, after Defense Secretary Jim Mattis resigned.

However, in order for Esper to be officially confirmed, he will have to step down from this current role, per the Federal Vacancies Reform Act of 1998. The law requires that someone being nominated for a job not currently be serving in an “acting” role, which would require a new acting SECDEF to take over while Esper awaited confirmation.

Shanahan served as part of a loophole, because he had previously been deputy SECDEF.

Esper was confirmed as Army secretary in December 2017, the third candidate the Trump administration put forward for the job. Trump said Friday that he plans to formally nominate Esper for the Pentagon’s top job.

“The surest way to deter adversary aggression is to fully prepare for war,” Esper wrote in his memo, sticking closely to the National Defense Strategy the department laid out under Mattis’ direction in 2018.

He also highlighted reform for “great performance and affordability,” an initiative he took head on while in charge of the Army, starting with a modernization overhaul codified with Army Futures Command.

In addition to acquisition reform, Esper made a name for himself with soldiers by tackling a litany of administrative requirements, from unmandated training to other check-the-block tasks ― like killing the legendary weekend safety brief and the much derided PT belt.

“One of the complaints is we’re doing all this mandatory training," he told Army Times in early 2018. “And when you look at the numbers, it is astounding how much it has grown over the years.”

Esper has also spearheaded changes to the Army’s enlistment requirements. Previously, a past of drug use or self-harm would ban a prospective soldier from joining, but he issued new guidance in 2019 that would allow a waiver if either occurred in early adolescence.

“You know, drug use or bad hearing, flat feet, eczema. I mean, all these things that tend to be disqualifiers,” he told Army Times in September. “I think we need to take a look at all those standards and make sure it’s still relevant for this day and age.”

And, at a time when the Pentagon hasn’t had an on-camera briefing from a senior official in over a year, Esper began quarterly, open-ended round tables with reporters.

In May, he encouraged Army public affairs to move more quickly and engage more with reporters, in the face of a reputation for slow responses and micromanaged statements.

“That has to change. Delays breed suspicious, which inevitably takes the form of skepticism, which often all but guarantees a negative spin to whatever we put out,” Esper said.

Public affairs professionals should engage the media constantly, he added, as should their commanders.

“In minor ways, I’d rather see us make mistakes than be perpetually behind the curve, or lose that trust with the media,” he said.

A timeline for Esper’s nomination and confirmation hearing has not been released, but he could officially take over the Pentagon as early as the end of July.