In Israel, which requires military service of its citizens, women in the vaunted Israel Defense Forces are restricted to serving in two light infantry border units when it comes to direct land combat.

These findings, among many others, are part of the Corps’ after-action report, one of 21 Marine studies and reviews released by the Pentagon after Defense Secretary Ashton Carter announced Dec. 3 that all combat jobs would be opened to women. He overruled the Marine Corps, which sought an exemption for infantry and commando units.

The Corps dispatched its Force Innovation Office to four nations — Australia, Canada, Israel and the United Kingdom — as part of the four military branches’ study about the impact of putting women into the infantry, armor and special operations forces. The Marines, by far, performed a larger number of assessments than the Army, Air Force and Navy.

In Australia, the Marine team found a defense force still grappling with its recent decision to open combat to women. It reported resistance to tough physical and mental standards for women from civilian leaders, who actually do the recruiting for the Australian Defense Force.

The report said the School of Infantry Commander “was concerned that abandoning traditional physical training routines was compromising the mental toughness of his students.”

Meanwhile, Canada’s lack of specific physical requirements for military occupations stands in sharp contrast to the U.S. armed forces, which require combatants to be able to complete a number of specific tasks, some of them grueling, to become an infantryman.

“Canadian soldiers repeatedly pointed to low physical standards as a significant problem,” the Marine report said. “Most commanders and soldiers agreed that introducing occupation-specific, operationally relevant combat arms standards would be very helpful to both keep soldiers fit and to demonstrate that women (should they meet the standard) could operate on an equal footing with men.”

The report noted that, decades after the women-in-combat ban was lifted, Canadian women make up less than one-half of 1 percent of enlisted infantry members and of combat engineers, and less than 3 percent of the tank force.

Conversely, there are myths about the roles that women play in the Israel Defense Forces, which feminists hail as a place where women can do anything.

The IDF this year decided to retain a ban on women serving in the confined quarters of a tank. Women are restricted to support roles in special operations and are limited to service in only two light infantry border units.

“Integration of female soldiers into the IDF ground forces is far more limited than popularly believed in the U.S.,” the Marine Corps visitors found.

The IDF also does not hold women to the same standards. It practices “gender norming” in physical tests, as opposed to Mr. Carter’s pledge that standards will be the same for both sexes, or “gender neutral.”

IDF women have to be able to carry 30 percent of their body weight, but men must carry 70 percent.

The Marines interviewed a female officer and a male general, both of whom talked about keeping men and women in separate observation posts.

“Both leaders talked about the physical differences between men and women, and how important it was to monitor the soldiers closely so they did not hurt themselves,” the report said.

Men do not want to join the Caracal light infantry border patrol unit. Instead of a hoped-for 50-50 split, the battalion is 70 percent female.

Still, the female Israeli soldiers are “highly motivated.”

“Women are determined to succeed and to prove themselves alongside their male colleagues,” the Marine report said. “We spoke with two panels of young women, both officer and enlisted. The women very often sounded like young Marines, and the women talked about proving themselves to the men. As they proved they could accomplish the mission and be value-added to the team, the men accepted them in their combat roles.”

On Sunday, British Prime Minister David Cameron announced that he, like President Obama, has ordered the army and the Royal Marines to open all land combat jobs to women sometime next year.

Britain has studied the idea for years. Reports highlighted the increased incidence of injuries among women and the prospect that few will qualify for the gritty mission of closing in on and killing the enemy.

The U.S. Marine team visited the United Kingdom last year. Its report said British and European labor laws prohibit governments from putting workers in jobs that they know will lead to injuries.

“Evidence that female soldiers in the combat arms incurred a disproportionately high instance of serious injuries could invoke this provision, based on differences in the likelihood and severity of injuries,” the Marines concluded. “In such a case, allowing women to participate in ground close combat would be an act of negligence. Such a finding would force the British Government to exclude female soldiers from the combat arms.”

When Mr. Carter announced the end of male-only combat units Dec. 3, he acknowledged the physical differences between men and women and warned that some military occupational specialties thus will have only a few women.

“There must be no quotas or perception thereof,” he said. “Thus far, we’ve only seen small numbers of women qualified to meet our high physical standards in some of our most physically demanding combat occupational specialties, and going forward, we shouldn’t be surprised if these small numbers are also reflected in areas like recruitment, voluntary assignment, retention and advancement in some of these specific specialties.”

No female officer was able to complete the Marine Corps’ grueling Infantry Officer Course and join the combat arms.

Three Army women completed the Ranger School, a tough career-building exercise, but not a qualification for the special operations Ranger regiment.