The ERA failed ratification primarily because the vast majority of women didn't want to be included in a potential future draft.
However, without any formal debate or policy discussion, women somehow magically ended up in combat units.
There are even those among conservatives who believe that most of the women who volunteer to be in combat units are most likely dykes who would be good killing machines. I doubt that is true.
I remember back when "The Love Boat" was a thing where women in the Navy who joined for free college or something, got themselves knocked up in order to avoid going to war in the Middle East. Some fighting machine!
Some female history in the military.
Public Law 90-130, signed by President Lyndon B. Johnson on Nov. 8, 1967, removed promotion and retirement restrictions on women officers in the armed forces. Thereafter, it was possible for more than one woman in each service to hold the rank of colonel and for women to achieve general (or flag) officer rank.
Just two years later, President Richard M. Nixon selected two women for promotion to brigadier general: Col. Anna Mae Hays, chief of the Army Nurse Corps, and Col. Elizabeth P. Hoisington, director of the Women’s Army Corps. These promotions were done simultaneously on June 11, 1970, in recognition of their equal importance.
PL 90-130 also eliminated the two percent limitation on WAC numbers – permitting WACs to serve in the Army National Guard. At this point, only prior-service women were allowed to join, due to the war in Vietnam demanding so much money that none was available to train women for enlisted Guard service.
As the war in Vietnam drew to a close and the Army began transitioning to an all-volunteer force, the role of women in the Army expanded to help fill vacancies before the draft ended in June 1973. In 1971, women with no prior-service experience were permitted to enlist in the National Guard. When estimates for male recruits revealed a looming shortfall in volunteers, Secretary of the Army Robert F. Froehlke approved a major expansion in WAC strength and the opening of all military occupational specialties to women in August 1972, except those that might require combat training or duty. This was the realization that women could be utilized in far greater capacity than ever before. That same year, the ban on women commanding units that included men was lifted.
This time period also marked the beginning of other advancements for women. Army regulations for the first time permitted women to request waivers for retention on active duty if married and pregnant, April 9, 1971. In that same year, the Army chief of staff authorized WACs’ entry into male drill sergeant schools and NCO academy programs.
The advent of the all-volunteer force in 1973 made a large difference in the numbers of women coming into the Army and Reserve components. As a result of recruitment, training and greater opportunities, the total number of WACs in the Army increased from 12,260 in 1972 to 52,900 in 1978.
Women entered the Army Reserve Officers Training Program (ROTC) beginning in September 1972, and the first female ROTC cadets graduated from South Dakota State University on May 1, 1976. Prior to this, the primary source of commissioning was the Junior College Women’s Program.
In 1975, the Army chief of staff approved the consolidation of basic training for men and women when test programs showed that “female graduates met the standards in every area except the Physical Readiness Training Program,” which could be modified without compromising the value of training. By 1977, combined basic training for men and women became policy, and men and women began integrating in the same basic training units on Fort McClellan, Alabama and Fort Jackson, South Carolina, in September. Similarly, the first gender-integrated class began with the Military Police One-Station-Unit Training at Fort McClellan on July 8, 1977.
Between 1975 and 1979, many Army rules and regulations concerning women changed and the standards for men and women in the Army began to equalize. The defense secretary directed the elimination of involuntary discharge of military women because of pregnancy and parenthood, June 30, 1975. Mandatory defensive weapons training was initiated for enlisted women and they were authorized to serve the same length of overseas tours as men – increased from 24 months to 36 months for single females. Effective April 1, 1976, the minimum age of enlistment of women was reduced to the same as for men, and by October 1979, all enlistment qualifications became the same for men and women.
Another major advancement for equal standards between men and women in the Army came in October 1975, when President Gerald Ford signed Public Law 94-106 that permitted women to be admitted to all service academies beginning in 1976. In 1980, the first women cadets graduated from U.S. Military Academy, West Point, New York. Since then, women have continued to enter every class there.
https://www.army.mil/women/history/