Initially a controversial choice for Treasury Department secretary, having promoted the credit default swap system that led to the 2008 financial crisis during his time at Goldman Sachs, Steve Mnuchin has grown into one of the most stable forces in President Donald Trump’s cabinet.

Since taking office, Mnuchin has kept away from scandal and managed to stay in the good graces of his boss amid record turnover of senior administration officials at the cabinet level, earning a reputation on Wall Street as a calming force, and one among foreign adversaries as a tough sanctions enforcer.

Mnuchin has been integral in orchestrating the reimposition of sanctions on Iran, after Trump withdrew from the 2015 nuclear deal negotiated between Tehran and six world powers, last May. Those sanctions will bring the Trump administration into conflict with some of America’s closest allies, which hope to preserve the nuclear agreement and their economic investments in the Islamic state.

But Mnuchin has grown used to confronting friends. While the Treasury secretary has tried to avoid press and responsibility in the White House’s growing trade wars with Europe, China and its continental neighbors, he is on the forefront of the effort to negotiate what the president deems “fairer” bilateral trade agreements worldwide.