When women make the news because of terrorism, the focus has often been on their role as victims or as potential allies in countering the threat.
By contrast, women who take part in and support extremism have sometimes been overlooked.
This changed when runaway teenager Shamima Begum was described as the "poster girl" for Islamic State after being tracked down at a Syrian refugee camp.
Four years ago, she left the UK with two friends to join IS, but claims she was "just a housewife".
Women in extremism
Ms Begum's case has raised a number of questions on women's active and willing participation in violent extremism both in IS and other groups.
A number of Rusi-backed studies and others have investigated the roles women play in organisations such as IS and al-Shabab, one of the deadliest militant groups in Africa.
Researchers interviewed women who had been directly or indirectly involved with al-Shabab's activities, to find out how they were recruited, and the impact that taking part in violent extremist activity has on women.
The work was conducted by academics in Kenya, who were able to use their long-standing experience and networks within communities identified to be at risk of radicalisation.
IS v al-Shabab
The roles played by women vary between groups.
Women in al-Shabab have often held what could be seen as more traditional roles, as wives of fighters and domestic help. They are also sometimes made to work as sex slaves.
They can also help attract new members. One study in Kenya discovered women were lured by others who promised them jobs, financial support and counselling.
For example, Hidaya (not her real name), a dressmaker, was recruited by a client who offered to invest in and expand her business. She was persuaded to travel to a border region, from where she was smuggled into Somalia.
Within IS, women often recruit - especially online - and play an active role in projecting the group's beliefs.
In Shamima Begum's case, her recruitment could be seen by IS as a propaganda victory, despite her suggestion that she had done little more in Syria than take care of her husband and children.
Women under IS are also allowed to serve as doctors and healthcare workers, with certain restrictions, while the group has an all-female morality police force.
However, differences between groups have become increasingly blurred as organisations become "inspired" by each other.
In Somalia, where al-Shabab is attempting to establish an Islamic state governed by Sharia (Islamic law), cases of female frontline or suicide fighters have also been seen.
Analysis of al-Shabab suicide attacks between 2007 and 2016 found 5% were carried out by women.
This is also the case in other parts of Africa, such as Nigeria where militant Islamist group Boko Haram has used women as suicide bombers.
Why do women join jihadist groups?
There are a number of factors driving women's recruitment into these groups.
To an extent, it appears that what motivates men also works for women, such as the pull of strong ideology and financial benefits.
However, tactics aimed specifically at women also emerged, such as the appeal of returning to traditional gender roles.
For instance, one of our studies indicated al-Shabab recruiters preyed on the insecurities of some young Muslim women who feared that higher education would delay their marriage prospects.
"If I get a man who will marry and protect me, why should I stress myself with studies or education?", one Nairobi University student asked researchers.
Others appear to have been initially attracted by promises of jobs, money and other opportunities.
However, discerning their motives for joining is difficult. Many of the women we interviewed claimed they had been recruited against their will.
Like Shamima Begum, some claimed they either weren't actively involved in the group's activities, or else took part against their will. Some say they were victims.
While some are likely to have been coerced in some form, denying responsibility is a useful way to try to reintegrate back into the larger community.
The road to rehabilitation
There are a number of rehabilitation approaches applied to former or returning fighters, but few that are aimed specifically at women.
Policymakers and security services need to take the specific issues women leaving extremist organisations have into account when devising prevention, rehabilitation and reintegration strategies.
For example, many will have had children with dead or absent fighters, while others will require counselling for trauma stemming from rape and sexual assault.
It is critical that governments address these issues when engaging with the female role in violent extremism. This would start with better understanding of how gender-based differences fuel women's involvement and the specific impact it has on their lives.
This would benefit their communities by managing the risk they present and helping to prevent more women from joining extremist groups.
About this piece
This analysis piece was commissioned by the BBC from experts working for an outside organisation.
Gayatri Sahgal is a research manager at Rusi.
The Royal United Services Institute (Rusi) is an independent think tank specialising in defence and security research.
Edited by Eleanor Lawrie