Dark clouds of war are gathering once again. Military posturing among major powers has increased and spending on ever more sophisticated and deadly weapons systems is soaring. The tone of debate and threats of action on display at the UN General Assembly in New York this week has done little to calm matters.

Yet away from the bellicose rhetoric, the truth remains that since the end of the cold war, wars between states have almost disappeared. In their place, armed conflicts within states have become the big threats to global peace and security.

Intrastate conflicts are nothing new. What is new is that they dominate the global security agenda for the first time in human history. Today, virtually all battle-related deaths and injuries are caused by intrastate armed conflicts.

The problem is that we have no collective security system that applies specifically to such conflicts. The UN charter was created to deal with relations between, not within, states. In fact, the present charter explicitly excludes interferences in the internal affairs of nation-states. This creates a legal void that has made intrastate armed conflicts and foreign interventions, as in Syria, so exceptionally brutal.

It is time we developed a set of international laws and norms for intrastate relations, as we did for those between states at the end of the second world war. Placing intrastate relations under a collective security regime would help prevent the unilateral foreign interferences and military interventions that have done so much damage.

At the root of these conflicts are failing nation states. Dysfunctional states are a huge problem as they create a vacuum in which armed non-state actors can thrive. These not only include the usual suspects such as al-Qaeda, Isis, the Taliban or Boko Haram, but also various rebel groups, secessionist movements, irregular militia forces and transnational crime syndicates.

The US-led military air campaign against Isis in Iraq and Syria will not change this. It may even mislead us to believe that we are getting to grips with this complex problem by simply applying superior military technology.

But as Afghanistan, Iraq, Syria, Libya or Yemen show, military interventions have only made local conflicts bloodier, last longer and solutions more difficult. They have contributed to the further collapse of nation states, playing into the hands of those we want to eliminate.

While today’s tensions between the west, Russia and China appear to announce a return to cold war thinking, the problems of failing nation states, belligerent non-state actors and resulting intrastate armed conflicts is likely to dominate our future. Population pressures, climate change, injustices and bad governance are factors that are likely to accelerate state failure, strengthen non-state actors and trigger more intrastate conflicts. We could tumble into a global chaos in which ever larger regions become ungovernable and are left in the hands of radical and criminal non-state actors.

The impact of this would be enormous. It was a non-state actor — and not a competing state power — that challenged the US’s superpower status on 9/11 and drew it into a series of costly and unwinnable wars. What would happen if some of these non-state actors get access to even rudimentary weapons of mass destruction? Terrorist attacks and mass migration to Europe may only be the tip of an iceberg that is heading our way. We need functioning nation-states to maintain peace and security — not despite, but because of, globalisation.

So, instead of spending trillions of dollars to enable the military to fight interstate wars, we should strengthen the UN to enable us collectively to deal with intrastate armed conflicts. For this, we need to rescue the nation-state.