The hard truth is that we don't fully know. There is no doubt that South Vietnamese women visibly participated in the war as frontline soldiers for the PLAF (People's Liberation Armed Forces, the armed wing of the NLF) and in support roles. Their involvement was not limited to waging war but they were also involved in revolutionary politics with the most visible and most internationally known at the time being Nguyen Thi Binh who was present during the Paris Peace Accords as a representative of the NLF.

There has been considerably little research done on the incredibly interesting topic of women PLAF soldiers and what has been done, such as Vietnamese Women at War: Fighting for Ho Chi Minh and the Revolution by Sandra Taylor (University Press of Kansas, 1999) is incomplete at best and has limited quantitative data. Historian Karen G. Turner claims that one-third of the PLAF consisted of women, but does not give an estimation on how many of them fought as soldiers and how many belonged to Main Force units as opposed to Local Force units. Therefore, it is hard to say whether or not it was more common for women to fight as soldiers or for women to act in a supporting role. Taylor's research has documented many narratives involving women combatants through interviews with surviving veterans. Many more of these interviews have been conducted over the years to add to an increasing reservoir of narratives by women fighting both for the PLAF and the PAVN (People's Army of Vietnam, the North Vietnamese Army). More narratives can be extracted from interrogations with women PLAF defectors which are available in American archives and other contemporary sources in English. From these, a reoccurring concept is that of the all-women unit. Women were not segregated into units based on gender, but the existence and constant references to all-women units suggests that there were enough women to build everything from squads to entire companies. Furthermore, women served as officers and non-commissioned officers which would have made them visible to male and female soldiers alike.

The women you claim to have seen in pictures were most likely not part of the PLAF. Instead, the most common visual depiction of women soldiers were North Vietnamese women who were part of North Vietnamese militias and the Youth Shock Brigades. There has been considerably more research into North Vietnamese women, something which reflects the visual depiction of them. According to Turner, 70,000 women served in support roles in the PAVN and that after 1969, women could also serve as soldiers. Less than 10,000 female soldiers served in the PAVN. Despite this, it's the women in the militas or the Youth Shock Brigades who still to this day remain the most widely depicted women fighting for North Vietnam and the cause of the NLF. Although the militias never saw fighting in the south and were primarily responsible for their immediate local areas, they were still visible as Anti-Aircraft gunners and participated in capturing downed American pilots, such as in the famous photograph from 1965 of the captured American pilot William Robinson being marched off by Nguyen Thi Kim Lai. The Youth Shock Brigades worked on the Ho Chi Minh trail and although they didn't see direct action with American soldiers, they were the constant target of American bombs which led to a direct confrontation for these women with death and injuries on the battlefield. Women, like men, were also tasked with defusing bombs and landmines. Added to this, the women in the Youth Shock Brigades suffered from the same ills that soldiers fighting in South Vietnam suffered: disease and hunger were common, but also sexual abuse. Likewise, they also suffered the consequences of their participation in the war in the post-war Vietnam from the wounds and diseases they suffered as well as traumatic memories.

The Vietnam War temporarily changed pre-existing gender roles in North and South Vietnam. Although traditional gender roles did continue in civilian life, women's participation in the war shocked male soldiers who met women that were armed, wore uniforms and questioned their male superiors. Although more than capable of fighting on equal terms as men, something evident in the track record of women in South Vietnam, the women who fought on the Ho Chi Minh line were looked down upon by male soldiers who did not think that women had a place in dangerous areas and wanted to protect them from harm and from harming their femininity (and the traditional concept of womanhood). As Turner writes: "A journalist on the Trail, for example, noted that soldiers taunted young women volunteers pushing heavily loaded pack bicycles up steep trails - "Be careful or you'll destroy your sex." In the post-war world, traditional concepts about the woman's role in Vietnamese society returned and motherhood became the primary purpose of a woman. Turner again: "In the face of official and popular messages that glorify the mother, women veterans cannot forget that no matter what their wartime accomplishments, in civilian society, they will be measured by their reproductive success."

Sources:

"Death and Suffering at First Hand": Youth Shock Brigades during the Vietnam War (1950–1975) by François Guillemot in Journal of Vietnamese Studies, Vol. 4, No. 3 (Fall 2009), pp. 17-60.

Inside the VC and the NVA by Michael Lee Lanning and Dan Cragg (Texas A&M University Press, 2008).

"Vietnam" as a Women's War by Karen G. Turner in A Companion to the Vietnam War, ed. Marilyn B. Young and Robert Buzzanco (Blackwell Publishing, 2002).

Vietnamese Women at War by Sandra C. Taylor (University Press of Kansas, 1999).