This report highlights the value of gender diversity, in particular women’s inclusion, for effective decision-making in defence and security contexts. Studies across various fields show that women’s participation often leads to more collaborative, less confrontational decision-making, reducing escalation in crisis situations. However, military culture and gender biases present barriers to fully integrating women’s voices and limit the potential to realise women’s positive influence on decision-making. To address this, research indicates that prioritising women in leadership roles can enhance team dynamics and reduce gender penalties, contributing to improved decision-making.