Mike Pompeo will arrive at the state department with two assets in the eyes of his new staff. He is not Rex Tillerson and for the time being he seems to have a rapport with the president.

The outgoing secretary of state was choked and emotional as he said goodbye to colleagues, but there were few noticeable tears among its employees. The air in the corridors of the vast headquarters in Foggy Bottom was cautiously cheerful.

Tillerson is held responsible among many of the nation’s diplomats for running the state department into the ground. He failed to defend it against severe cuts to its budget, and allowed the majority of senior posts, along with over 40 ambassadorships, to go unfilled.

Considering he was supposedly brought on board for his corporate experience, Tillerson appeared to be a poor manager. Most specialists and department heads felt undervalued and excluded from decision-making, which was monopolised by a small clique around Tillerson.

Pompeo by comparison comes with generally high approval from the CIA where he was seen as a champion of the agency, and an effective manager. He also appears to have the president’s ear, and for his staff at the state department and his foreign counterparts, that represents a distinct improvement. They can have reasonable confidence that when Pompeo speaks, he will represent the president in ways that Tillerson seldom did.

The downside is that the diplomats, US and allied, may not like what they hear. Tillerson provided an element of continuity in US foreign policy, and at least some restraint or counter-weight to some of Trump’s impulses, on Iran, Russia, North Korea, trade and climate. In most cases that will change. Pompeo has shown himself to be a loyalist before all else.

The question remains: how long can such total loyalty survive the requirements of leading the nation’s diplomats? Here is where Pompeo stands on the department’s most pressing issues:

Iran

The 2015 nuclear deal with Iran, the Joint Comprehensive Programme of Action (JCPOA), is the one issue on which Tillerson did seem to have real mitigating effect on Trump, persuading the president not to walk out of the deal he despised for more than a year. The JCPOA now looks likely to fall victim to this week’s reshuffle.

Trump has demanded that Congress and the European allies “fix” the deal before he agrees to sign another waiver keeping US sanctions suspended. The trouble is that the other six national signatories – including the UK, France and Germany – insist the JCPOA cannot be renegotiated. In an attempt to square this circle, diplomats from the three European partners have been meeting state department officials to come up with ideas on how to address Trump’s grievances – that the JCPOA has sunset clauses on some of its elements, and does not include limits on missiles – while keeping the deal intact. The next such meeting is on Thursday this week.

Tillerson was a supporter of the JCPOA, but Pompeo has consistently treated it with scorn, mirroring the president. With a secretary of state uninterested in saving the deal, cooperation with the Europeans could crumble along with hopes of a face-saving solution. When Trump is next due to sign a sanctions waiver, there will be little to stop him refusing. That could destroy the JCPOA, lead to a major transatlantic rift with European allies and rekindle a nuclear crisis in the Middle East.

North Korea

Tillerson was an advocate of contacts with Pyongyang, but was frequently undermined and disowned by the White House. Trump opposed talks until he was invited to a summit last week by Kim Jong-un. Even then, he has shown little inclination to draw on state department experience and expertise in preparing for the encounter, which is supposed to take place by the end of May.

He may be more prepared to trust Pompeo and therefore collaborate with state department diplomats. But Pompeo’s hawkish views, including thinly-veiled calls for regime change, could deepen North Korean distrust and act as a barrier to any follow-on talks after a summit. And if Pompeo has by then helped Trump blow up the JCPOA with Iran, there would be even less reason for Pyongyang to believe any deal it struck with the US would last.

Russia

During the 2016 election campaign, Pompeo - then a highly partisan Republican congressman - gleefully tweeted about the stolen Democratic Party emails published by Wikileaks. Since taking the helm at the CIA, which is part of the general US intelligence consensus that the hacked emails were part of a Russian campaign to skew the 2016 election, Pompeo’s views have changed. He has said America “has an obligation to push back” against Russian adventurism in Syria and Ukraine. As secretary of state, he may have to choose between his determination to push back, and his rapport with Trump.