As tensions between countries are ever increasingly spilling over into cyberspace, whether it be direct nation state attacks or indirect through non-government affiliated APTs, the need to countries to defend their critical infrastructure has never been more important. One key method that countries utilize to prepare for a potential attack, is to engage in live fire cyber defence exercises. These exercises are intended to prepare a countries national organisation for cybersecurity, alongside select industry participants, for a potential nation state attack against their infrastructure. This talk explores the world's largest and most advanced live-fire cyber defence exercise, and the speaker's personal experience of participating in it.