Trump’s pardon of the Blackwater murderers is not universally popular.

The UN Human Rights Office warned that the pardons would serve to embolden others to commit similar crimes.

The father of a nine-year boy who died said Mr Trump “broke my life again”.

It was an example of following that awful slogan “Do it to them before they do it to you.”

The story told to me by eyewitnesses followed a familiar pattern: in the heavy traffic a frightened and inexperienced driver ignored warnings to stop, and carried on towards a convoy of American officials protected by Blackwater agents.

Several witnesses insisted that the contractors had panicked and opened fire indiscriminately. Among those who died was a nine-year-old boy who was sitting in the back of his father’s car and was hit in the head.

Again and again during the war in Iraq I witnessed lesser versions of the Nisoor Square incident, when American soldiers and contractors assumed they were being fired on, and retaliated in devastating and often uncontrolled fashion.

But Nisoor Square had a particularly powerful effect on Iraqi opinion which persists to this day.

By pardoning the four men involved, President Trump has reignited the hatred and resentment caused by the incident.

Trump feeds on hatred and resentment. It’s what gives him life.