Gender is widely recognized as an important and useful lens for the study of International Relations. However, there are few books that specifically investigate masculinity/ies in relation to world politics. Taking a feminist-inspired understanding of gender as its starting point, the book: - explains that gender is both an asymmetrical binary and a hierarchy; - shows how masculinization works via 'nested hierarchies' of domination and subordination; - explores the imbrication of masculinities with the nation-state and great-power politics; - develops an understanding of the arms trade with commercial processes of militarization. Written in an accessible style, with suggestions for further reading, this book is an invaluable resource for students and teachers applying 'the gender lens' to global politics.