In 2011, the International Atomic Energy Agency (IAEA) released the fifth revision of its Nuclear Security Recommendations on Physical Protection of Nuclear Material and Nuclear Facilities. This update of IAEA nuclear security guidance was a significant improvement upon its predecessors, suggesting new and strengthened approaches to nuclear security in a range of areas. Nearly a decade later, however, the global nuclear security landscape has changed. Nuclear security regulations and practices have improved. International institutions and norms supporting global nuclear security architecture are stronger. Countries have made new political commitments to strengthening their nuclear security. Legally binding agreements are more widely subscribed than they were before. Meanwhile, new global threats have surfaced, presenting new challenges to physical protection systems. A range of emerging technologies creates new opportunities, but also new risks.