For the past 20 years, the notion of bioterror has been a source of considerable fear and panic worldwide. In response to the terror attacks of 2001 in the USA, extensive research funding was awarded to investigate bioterror-related pathogens. The global scientific legacy of this funding has extended into the present day, highlighted by the ongoing COVID-19 pandemic. Unsurprisingly, the surge in biodefence-related research and preparedness has been met with considerable apprehension and opposition. Here, we briefly outline the history of modern bioterror threats and biodefence research, describe the scientific legacy of biodefence research by highlighting advances pertaining to specific bacterial and viral pathogens, and summarise the future of biodefence research and its relevance today. We sought to address the sizeable question: have the past 20 years of investment into biodefence research and preparedness been worth it? The legacy of modern biodefence funding includes advancements in biosecurity, biosurveillence, diagnostics, medical countermeasures, and vaccines. In summary, we feel that these advances justify the substantial biodefence funding trend of the past two decades and set a precedent for future funding.