Three ways to end conflict As war spins out of control, what might happen next?

Brinkmanship, the ability to take a country to the edge of war without plunging into the abyss, was always the staple of cold war diplomacy, associated with John Foster Dulles, the US secretary of state in the 1950s.

- Patrick Wintour Diplomatic editor

But now in more unstable times - where the line between state and non-state actors has blurred, and weapons of war diffused - the world this week finally tipped over the edge, and suddenly it is in freefall.

The first week of the war came at a cost of $13bn (£9.75bn) to the US, but now as much as $200bn is being sought by the Pentagon. Oil at $125 a barrel is no longer an Iranian, or Russian, fantasy. The crown jewels of Qatar - its Ras Laffan liquified natural gas plant - may not reopen fully for five years - and other oil depots from Bahrain to Abu Dhabi are exposed to Iran's low-cost drones. Then add the human cost of 18,000 civilians injured and more than 1,300 killed in Iran alone.

Iran, fighting for its national survival and aggrieved that Europe will not assert each day this is a war that America started, had long warned it would retaliate by attacking US bases in the region, yet somehow the US president, Donald Trump, seemed surprised. Inured to decades of isolation and condemnation, the late supreme leader Ali Khamenei explicitly warned at the beginning of February: "The Americans should know that if they start a war, this time it will be a regional war," in the process burning every diplomatic bridge with its Arab partners.

Equally, Iran said a new phase of the war would start if its energy facilities were attacked. Ali Larijani, the recently assassinated Iranian security chief, was one who gave that warning most explicitly to the Gulf states, and tried to persuade them their national interest did not lie in siding with Israel. But he was being given a martyr's funeral on Wednesday in Tehran just as the world's largest gas-to-liquids plant, Pearl GTL, was struck.