The war began 15 years ago this Sunday, "9/11", when four attacks by al-Qaeda killed 2996 people, injured a further 6000 and caused US$10 billion worth of damage.
These acts shocked everyone. The global community had been familiar with terrorism, as in non-state actors intentionally targeting civilians, since the turn of the 20th century. Hijackings, bombings and assassinations had become a common currency of groups such as those related to the liberation of Palestine, Ireland or the Basque country in Spain.
Such groups, left wing and nationalistic, were easy to understand. As terrorists with political goals they wanted to achieve in the temporal realm, there were limits on what they were willing to do. The disintegration of the Twin Towers challenged all of these assumptions.
President George W. Bush responded to attacks by declaring a "War on Terror". Fifteen years after this declaration was made there are nine times more people killed in terror attacks each year than there were before the war was declared.
Since the year 2000, there have been more than 61,000 terrorist attacks, killing more than 140,000 people. Last year, 28,300 people were killed by terrorists. Five countries, namely Iraq, Nigeria, Afghanistan, Pakistan and Syria, accounted for 78 per cent of all of these terror killings.
Only 5 per cent of the global terrorist-related death occur in the countries we are closest to. When Paris, Orlando, Brussels or London is attacked we all watch, as we did when New Zealand recorded its first conviction of a potential terrorist, and he was taken from the court room shouting "Allah Akbar".
Unless things change, we need to prepare for more terror in coming years, not less.
To defeat the terrorist in the 21st century requires an entirely new way of thinking. The terrorist is no longer a left-wing, nationalistic ideologue. Today, the most powerful terrorist groups are driven by religion and, in particular, deviations from the Sunni branch of Islam. Islamic State, Boko Haram, the Taliban, al-Shabaab and al-Qaeda are all linked by this common strand.
The challenge is no longer just about economic poverty, but also cultural alienation. Fighting these people requires us not only to think deeply about what values we are defending, but to also work closely with the overwhelming majority of 1.2 billion Muslims who share the values of the modern world and have no tolerance for the hatred the terror groups espouse.
We need to be prepared for horror and be resilient, and measured in response, when the next act of terror occurs.
Despite the excellent work of the security services, we are fighting an enemy who is continually looking for gaps in the defences, and who abides by none of the international standards that human civilisation has built up over the past 3000 years.
For groups such as Islamic State, there is no crime of war or crime against humanity that they have not breached. From committing genocide against entire ethnic groups like the Yazidi, through to the intentional destruction of World Heritage sites, these people are without restraints.
They are also exceptionally innovative as they compete amongst each other to achieve records of civilian deaths and/or attacks of symbolic importance.
Before September 11, security services could foresee that planes could be hijacked or bombs placed upon them, but they could not foresee that the plane, or the terrorist, would become the weapon.
Terror groups did not use suicide bombings before the 1970s. By the 1980s they were one per year, they then progressed to being one per month, to one per week, to now, where the rate is one per day.
We need to be thinking long term. Outside of our border, terrorism spills from countries which have either completely failed or in which lawlessness is rife. Finding peace will require rebuilding failing or failed states to be places of stability in which human rights, the rule of law, economic opportunity and environmental sustainability are real.
Rebuilding countries such as Syria, Iraq, Somalia, Libya or Yemen will take decades. Fifteen years on, Afghanistan has not yet created a stable country.
Inside of our border we must all work to ensure communities of inclusion and tolerance, based around the values which define our society. Unless we are prepared to invest for the long term both domestically and internationally, we will not progress past the end of the beginning of the War on Terror.
Alexander Gillespie is a professor of law at the University of Waikato.