An abundance of retrospectives and eulogies marking September 11th, some insightful, others pro forma, filled the airwaves and print media commemorating the 20th anniversary of the destruction of New York’s Twin Towers and part of the Pentagon’s second wing. But despite this outpouring, every commentary seemed to have missed the most crucial consequence of that disastrous day. That was not the global war on terror that shortly followed or the ill-conceived invasion of Iraq over weapons of mass destruction that did not exist eighteen months later. Instead, what September 11 wrought was the final demise of the Westphalian state-centric system that had dominated international politics since 1648. To some, the Westphalian system seemed an abstraction of largely academic value. But that was akin to believing gravity was an abstraction with little practical application. 20 years later, 9/11’s implications are still not fully comprehended. The international system was dependent on individual states for its conduct, regulation and matters as vital as war and peace. Sovereign states were the ultimate, legitimate arbiters of force. More often than not, international authority and influence and the overall power of a state were commensurate. The implosion of the Soviet Union did not alter this equation; it simply made the US more influential until September 12, the day after. The Al-Qaeda attacks demonstrated that non-state actors and stateless organisations had the capacity and reach to deliver vast amounts of disruption and destruction, even against superpowers. One crucial difference from the past was that ironically as standards of living improved, modern societies became extraordinarily and even existentially vulnerable to disruption. These advances had also created greater potential weaknesses. The Westphalian system was akin to believing gravity was an abstraction with little practical application. Disruption of this scale was not new. Plagues, floods and droughts had long been catastrophic. Gavrilo Princip’s handful of bullets killed an archduke and his wife; igniting World War I in August 1914. However, today, society’s power grids, Internet, financial networks and basic services for food, water and fuel among others are massively vulnerable. In prior history, only states controlled the means to disrupt or destroy these and other vulnerabilities on a vast scale. After September 11, that condition no longer existed; effectively ending the Westphalian system of international politics. Why is this important? September 11 introduced a different era. Yet, no one seems to have recognised this reality. Since 9/11, Covid-19, violent global weather, massive cyberattacks and the continuing failure of governments to govern emerged as unmistakably disruptive symptoms of this post-Westphalian world. Indeed, a Fifth Horseman of the Apocalypse armed with a more virulent form of the Cold War MAD (for Mutual Assured Destruction and the spectre of thermonuclear armageddon) has arisen symbolising this profound transformation. The New MAD stands for Massive Attacks of Disruption whether caused by man or by nature. Unlike the Cold War MAD when nuclear war was deterred, the new MAD is not fully deterrable. At best, MAD can be partially prevented, contained or minimised. Seven major disruptors are among the major dangers posed by MAD beyond the current pandemic. The first is failed and failing government. Western democracies are now suffering from this malaise and its disruptive power. Despite deniers, climate change is potentially existential. The signs of climate change are impossible to ignore. Cyber and social media have enormous power to disrupt. Terror, especially as it assumes a greater domestic form, lurks. Last, two less obvious disruptors must not be dismissed: debt and drones. With the US debt approaching 150 per cent of the GDP, how will this be repaid? No one knows. And consider how drones will disrupt future society from undertaking helpful tasks to highly sinister and disruptive roles. Suppose the January 6 Capitol Hill rioters flew armed drones that are cheap and easy to build to strike both Houses of Congress? The US views its principal national security threats like China and Russia, the former economically and politically and both strategically and militarily. But the new MAD is at least as, if not more, dangerous certainly in practice than these two powers. Yet, no one has raised an alarm about MAD’s broader challenges; keeping focus only on Covid, climate and cyber threats. Continued myopia will not work. In early 1914, no one predicted looming calamity. In early 1939, few other than Churchill saw war. 2021 will not lead to a global conflict. However, the failure to acknowledge and respond to the Fifth Horseman armed with this new MAD could prove as cataclysmic as these two earlier inflexion points. But who is paying attention? The writer is a senior advisor at Washington, DC’s Atlantic Council and a published author