Since then, the NSC, which is divided between those working on policy and those dedicated to administrative and technical matters, has expanded over the course of nearly every presidency. After 9/11, the NSC grew exponentially as presidents tried to manage the wars in Iraq and Afghanistan. Congress also created a separate staff known as the Homeland Security Council. The George W. Bush NSC doubled over eight years to about 200, and when Barack Obama merged the staff with the HSC, it doubled again to more than 400, more than half of whom worked on policy.

Nearly everyone in Washington—former staffers, the military, the press, Congress—agreed that was too large. In a sign of just how unsalacious the Obama years were, the size of that staff became a scandal, with the NSC accused of micromanaging rather than coordinating government. Amid the uproar, Obama agreed to cuts: Susan Rice, his last national security adviser, launched a “rightsizing” in 2015 that eventually shrank the policy staff to fewer than 180 people in 2017.

According to Washington Bureaucracy 101, where someone stands depends on where he or she sits. Following that logic, one would expect O’Brien, who had little Washington experience when named national security adviser in September, to boost his influence with a strong and robust staff. That’s why even for those of us who have advocated shrinking the staff—in a history of the NSC published last year, I argued it was too big to be managed effectively—O’Brien’s quick decision to launch a drastic cut was surprising and seemed contrary to his interests.

At one of the first town-hall meetings with the 174-person staff he inherited, O’Brien summarily announced that dozens of positions would be eliminated within months. In an op-ed in The Washington Post and in public remarks, O’Brien explained that he wanted to make the staff “more effective by reaffirming its mission to coordinate policy and ensure policy implementation,” while also reducing redundancies between the NSC and government agencies. He also said, “The president has to have confidence in his NSC staff.”

John Gans: Robert O’Brien should have to face Senate confirmation

The national security adviser’s op-ed did not mention Obama holdovers, but they were clearly the target of that “confidence” line. O’Brien took over a staff that had been beleaguered by a years-long battle between Trump supporters and career officials deemed loyal to Trump’s predecessor. Given that the average length of NSC tenures is just one to two years, few holdovers were left three years after Trump’s inauguration. Still, O’Brien’s purge, which cut more than 60 policy staffers, was not about bringing peace to the staff, but finally winning the war at the NSC.

O’Brien’s urgency appears to have been driven as well by the fallout over the president’s scheme to pressure Ukraine for political dirt on a campaign rival. He began trimming staff just as the report by a whistleblower, who reportedly had ties to the NSC, became public and Congress launched its inquiry into the affair. That investigation and testimony by staffers such as Alexander Vindman, an Army lieutenant colonel loaned to the NSC to work on Ukraine, revealed deep resistance to the scheme by several on the staff.