The Marine Corps expects to soon have its first female infantry officer, a historic first following her anticipated graduation Monday from the service’s grueling Infantry Officer Course, said three military officials with knowledge of the training.

The lieutenant and her male colleagues completed a three-week combat exercise at the service’s training center in Twentynine Palms, Calif., on Wednesday, the final graded requirement in the 13-week program. The infantry course is widely seen as some of the toughest training in the military, with about 25 percent of all students washing out.

The class will mark its graduation Monday with a “warrior breakfast” 35 miles south of Washington, in Quantico, Va., where most of the course is conducted, the officials said. All three spoke to The Washington Post on condition of anonymity because the graduation has not yet occurred. All that remains between now and then is returning equipment used during training, and a few administrative days, they said.

This historic moment arrives nearly two years after then-Defense Secretary Ash Carter lifted the military’s last remaining restrictions for women, part of an effort by the Obama administration to make the armed forces fully inclusive. Officials shared few details about the lieutenant Thursday, and two said it is unlikely that she will agree to do any media interviews, preferring to be a “quiet professional” and just do her job.

The lieutenant will take over a platoon of infantry Marines in a service that is often seen as the most resistant to full gender integration. The Marine Corps was the only service to recommend keeping some units, especially those carrying out infantry and elite reconnaissance operations, closed to women ahead of the Pentagon requiring all jobs to be open to women.

The Marines first opened the Infantry Officer Course to women experimentally in 2012, allowing women to attempt it as a part of broader research across the Defense Department examining how to integrate all-male units. Thirty-two women attempted the course before the research ended in spring 2015, and none completed it.

Four additional female Marines have attempted the course since the Pentagon opened all jobs to women in 2015, including the lieutenant expected to graduate Monday. At least one of those four women attempted the course twice, but did not complete it.