The secretary of state had known a battle was brewing – but he had survived similar clashes with the president before

Rex Tillerson’s last significant act as secretary of state was characteristically out of tune with the White House.

Donald Trump’s spokeswoman, Sarah Sanders, had avoided any blame of Russia for the poisoning of an ex-spy in Britain, but minutes later Tillerson issued his own statement, which was definitive in supporting the UK assessment that Moscow was behind the attack.

Trump fires Tillerson: president swings axe after series of policy clashes Read more

It was the sort of statement of unquestioning support for an ally that would be expected in more normal times, and that was the problem. Trump had said privately but repeatedly that he found Tillerson too “traditional”.

Most longstanding observers had expected there could be a tweeted rebuke from Trump on Tuesday morning, as there had been several times in the past when Tillerson had strayed from the White House line.

But the dismissal came as a shock nevertheless, at least to state department officials who had accompanied Tillerson on his final foreign tour, to Africa.

The exit was brutal. Trump phoned Tillerson from Air Force One soon after midday, more than three hours after the tweeted announcement of his firing.

Tillerson managed only to secure agreement for him to stay on formally until the end of March to oversee a transition.

State department officials had said earlier that he would leave his post immediately and could not confirm whether he would even return to pack up his belongings. A departure date of 31 March was agreed upon, but he relinquished day-to-day running of the department to his deputy, John Sullivan.

When he appeared to make his farewell at the lectern in the state department briefing room, he was clearly exhausted and emotional. His voice was on the point of cracking.

Play Video 1:05 Rex Tillerson: 'I'll return to private life proud to have served my country' – video

He focused on the selflessness of public service and did not mention the president. He spoke about the values of accountability he had tried to instil in the state department, not the administration’s.

Tillerson and Trump’s offices even clashed about the circumstances of his departure. The White House said that he had been given a few days’ notice. But a Tillerson spokesman, Steve Goldstein, told reporters it had come as a complete surprise to Tillerson, soon after he landed in Washington at 4am.

Reporters at the state department were told that Goldstein would provide a briefing. Then Goldstein was said to have been “pulled aside into a meeting”. An hour later the news leaked that he had been summarily fired.

Tillerson had known over the weekend that yet another battle was brewing. He received a call on Friday from John Kelly, the White House chief of staff, according to the Associated Press, but that was apparently to warn him that there might be a tweet “of concern to him” in the pipeline.

But the veteran Texan oilman had survived similar battles before, riding out presidential dissatisfaction by marshalling his allies, and affecting a laconic unconcern about the backstabbing ways of Washington.

When White House officials unleashed a flurry of unattributable press briefings in late November suggesting that Tillerson was on the way out, he held an early morning meeting with James Mattis – the defence secretary and his close ally – and the two of them went for lunch with Trump.

After that meeting, the president disavowed any intention of getting rid of Tillerson, declaring it “fake news”.

That incident led to speculation that there was a “suicide pact” among traditional conservatives in the cabinet – including Tillerson, Mattis and possibly the treasury secretary, Stephen Mnuchin – in which they would all threaten to leave if one of them was threatened.

But if the pact ever existed, it failed to save Tillerson this time – perhaps because he was out of the country and unable to rally resistance. On the last leg of his African tour, he closed himself in his room for a day, claiming sickness, and then announced he would be leaving for home a day earlier than scheduled.

By the time his plane landed in Washington, it was too late: the execution by tweet followed just a few hours later.

Within minutes, Nikki Haley, the US envoy to the UN – who had pursued her own hawkish foreign policy in New York without reference to Tillerson or the state department – put out her own tweet. Haley described the reshuffle as a “great decision” and said nothing about Tillerson.

Nikki Haley (@nikkihaley) Congratulations to my friend and soon to be Secretary of State Mike Pompeo! Great decision by the President. 🇺🇸

Haley’s widest policy divergence from Tillerson was over the multilateral nuclear deal signed with Iran in 2015, which imposed strict curbs on the Iranian nuclear programme in return for sanctions relief. Tillerson had consistently advocated remaining in step with European allies in abiding by the deal.

By contrast, Haley and Pompeo have unfailingly channelled Trump’s distaste for the deal – which could well be killed off by Tillerson’s departure.

Trump must sign a waiver on sanctions in mid-May for the US to stay within the agreement. He has signalled he will not do so, and openly expressed his frustration that Tillerson had persuaded him to sign earlier waivers.

Russia was another important source of discord, though one that Trump – under investigation for possible collusion with Moscow – has less reason to advertise.

The reaction to the nerve agent attack in the UK was just the latest example. Throughout his tenure Tillerson stuck to a tough line on sanctions, insisting that they would not be lifted until Russia changed its behaviour – most importantly in Ukraine.

Trump, by contrast, has constantly sought ways to relax the sanctions, starting from the first weeks of the administration, before Tillerson’s Senate confirmation,when the White House drafted an executive order relaxing key anti-Moscow measures. It was only stopped by firm resistance from state department staff and allied capitals.

On North Korea, Trump had humiliated Tillerson by tweeting his lack of confidence of the secretary of state’s diplomatic efforts to resolve the crisis over Pyongyang’s nuclear and missile programmes. The president told him not to “waste his time”.

Donald J. Trump (@realDonaldTrump) I told Rex Tillerson, our wonderful Secretary of State, that he is wasting his time trying to negotiate with Little Rocket Man...

And when Saudi Arabia and its Emirati allies imposed a surprise embargo on Qatar in June, Trump immediately took Riyadh’s side while Tillerson criticised the Saudi ambush and tried to broker a solution.

Time and again, he was blindsided and sidelined in the Middle East by Trump’s son-in-law and special envoy, Jared Kushner, who is reportedly under scrutiny by Robert Mueller for mixing the interests of his family’s real estate business.

Tillerson and Trump also grated personally. Trump saw the Texan as staid while Tillerson saw his boss as brash and ill-informed. He reportedly threatened to resign in July after Trump gave a highly politicised speech to the Boy Scouts, an organisation Tillerson used to run.

Rex Tillerson says he won't quit but doesn't deny calling Trump a 'moron' Read more

After a security briefing on nuclear weapons in the same month, when Trump demanded to know why the US could not restore its arsenal to cold war levels, Tillerson described the president in his absence as a “fucking moron” and the comment got back to Trump.

When the report surfaced in October, Tillerson did not deny it. Trump appeared to shrug off the insult, bragging he could beat Tillerson in a IQ contest – but it is unlikely it was forgiven.

Trump and Tillerson never took much time to find out whether they had similar worldviews. Their first meeting in Trump Tower in New York was in December 2016, after Trump’s shock election win.

Play Video 2:05 Trump and Tillerson: the end of a rocky relationship – video

Tillerson, the outgoing head of ExxonMobil, thought he was just being asked to give his general views on foreign policy, and was taken aback when the president-elect offered him the top diplomatic job on the spot.

He later said he was reluctant to take the post, and had been looking forward to retirement, but had been persuaded by his wife.

Once confirmed, he approached the job as a commercial executive, telling Congress his focus was on the restructuring of the state department.

The restructuring took the form of a drastic downsizing. The White House proposed a cut amounting to about a quarter of the departmental budget, and Tillerson did little to defend his department, alienating many of his diplomats and civil servants.

Rex Tillerson: hapless, hopeless and tragic. Now his time is up | Richard Wolffe Read more

Forty-four ambassadorships are unfilled with no nominations, and with Tillerson’s departure eight out of the nine top state department administrative positions are unoccupied. Staff also felt locked out of decision making, which was increasingly concentrated in the hands of a small policy planning unit.

Week by week, the state department became less relevant in Washington and in the rest of the world, either because it had fewer diplomats to dispatch, or less interest in multilateral diplomacy. It evidently did not have the ear of the president.

That erosion of influence, of what was the world’s mightiest diplomatic institution, is likely to be Tillerson’s most lasting legacy. And very few, if any, believe it will be reversed by his successor.