About 12,900 cadets attend the Army, Navy and Air Force academies that train future officers to lead America's vast military.

Every other year, they are given the chance to fill in an anonymous survey about unwanted sexual contact or sexual assaults.

According to the figures from 2018, 747 people reported some sort of sexual assault -- up from 507 in 2016, an increase of more than 47 percent.

"We find these results to be frustrating, disheartening and unacceptable," said Elise Van Winkle, who heads a Pentagon personnel and readiness department.

The biggest increase was noted at the Army's West Point Academy in New York, where 16.5 percent of women reported some sort of sexual assault, up from 10.2 percent previously.

In a statement, the Army's senior leaders said the report was "troubling and disappointing."

"This is not just about the Army staff and faculty at West Point -- we also expect more from the cadets, who are our Army's future leaders," the statement read.

Increases in the past have been chalked up to a greater awareness of sexual assaults and therefore a better reporting of cases, but this year the Pentagon said the problem has deeper underlying drivers that still need addressing.

"The trends are a reflection of the pervasiveness of this misconduct and the difficulty in sustaining a culture change over time," Van Winkle said.

The report found the number of actual sexual assault cases reported to authorities hit a new high of 117, up from 112 two years earlier.

Nate Galbreath, deputy director of the Pentagon's sexual assault prevention office, said cadets often are unwilling to come forward because they are worried about how other students will perceive them.