BELTSVILLE, Md. — They consider themselves the most elite protection force in the world, as capable of taking a bullet for the president as investigating a complicated financial crime.

So when it comes to preparing new members for its ranks, the Secret Service has long made training a high priority. That has become more important of late, as the agency struggles to keep pace with painfully high attrition and the unrelenting workload that fuels it.

“They are in a vicious cycle,” John Roth, the inspector general for the Department of Homeland Security, said last month as he laid out the Secret Service’s personnel shortfall at a hearing on Capitol Hill. Mr. Roth estimated that the agency needs to increase by 1,700 employees in five years, to 8,200, if it is to properly perform its investigative and better-known protection missions.

The way out of that cycle passes though Beltsville, a suburb between Washington and Baltimore where the Secret Service’s training center occupies a 493-acre campus. Past a protected, unmarked gate, would-be special agents and uniformed officers confront simulations of nearly every threat. There are shooting ranges, classrooms, gyms and a mat room, but also a fake town filled with mock snipers, a replica Marine One presidential helicopter and acres of woods for special operations training.