(CNN) -- There were more than 1,300 complaints of sexual harassment in the military last year, according to a Pentagon report released on Thursday.
The report involving informal and formal complaints covered all of the military's major service branches and the National Guard.
Of the complaints, 59% were considered substantiated, meaning that follow-up action confirmed a finding of sexual harassment.
Sex harassment in the military is defined as a "form of sex discrimination that involves unwelcome advances, requests for sexual favors, and other verbal or physical conduct of a sexual nature" where the victim may perceive that rejection would hurt career advancement or impact their future pay.
A majority of the incidents took place on military installations, the report said.
The data covered the year-long period ending last September 30.
Most of those filing complaints were women from the enlisted ranks, and most of the allegations were directed at men operating in the same unit as the person claiming harassment, according to the report.
Nearly half of the complaints against men were made against senior non-commissioned officers.
"We have room to improve, we have room to grow," a senior defense official told reporters. "One is one too many and until we have zero, we haven't achieved success."
The findings come two weeks after a separate report released by the Pentagon showed the number of military sexual assaults had increased sharply year over year.
Defense officials attributed that increase largely to stepped-up reporting practices on the part of alleged victims.
Defense officials who addressed reporters on the sex harassment figures said the military would work to strengthen education, training and accountability programs.
Like sexual assault, the military believes harassment is often under-reported.