The Guardian | Julian Borger: Our world affairs editor reflects on how, despite years of negotiations, we came once again to the brink of conflict

Countries tend to go to war when diplomacy fails. But Washington and Tehran are now facing off because it succeeded. It was because the 2015 nuclear deal was Barack Obama�s proudest foreign policy achievement that Donald Trump was so determined to destroy it.

The US and Iran are sliding back towards the brink of conflict. If a missile had landed a little bit differently in the course of the latest exchange of hostilities, they would probably be at war by now.

As the pendulum has swung one way and then the other, the Guardian has tried to cover the diplomacy with the same depth and emphasis as the military manoeuvres, even when it seems slow-moving and complex.

When formal talks began between the Obama administration and the new government of Hassan Rouhani in September 2013, our foreign editor, Jamie Wilson, decided we should cover the whole process in detail because of the potentially historic nature of success, and the very high price of failure.

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