The appointment of veteran Kathleen Troia McFarland as deputy national security adviser confirms that President-elect Donald Trump will prioritise the threat of the Islamic State in Iraq and Syria (ISIS), analysts say.
Ms McFarland, who has a long record of national security experience, shares the same belief as her direct boss, national security adviser Michael Flynn, that ISIS is a significant threat to the US.
Both believe the administration of President Barack Obama has mishandled the threat and advocate a more robust approach to countering ISIS terrorism.
In campaign speeches and interviews, Mr Trump has harped on a plan to defeat ISIS but offered no details. Mr Flynn and Ms McFarland will be key to strategising and implementing the plan.
Ms McFarland, 65, a Fox News analyst and contributor on national security, previously worked under Republican president Ronald Reagan and former Cold War strategist Henry Kissinger.
She was a deputy assistant secretary of defence for public affairs under Mr Reagan, and helped write a groundbreaking speech in 1984 by his defence secretary Caspar Weinberger, which laid out a doctrine for US military interventions.
"She understands two things," said Mr Blaise Misztal, director for national security at the Bipartisan Policy Centre in Washington, DC.
"First, that the National Security Council is supposed to act as a coordinating body that presents the president with information and advice from all the departments and agencies involved in foreign policy; it is not the sole source of foreign policy decisions. Second... it is not enough to just be against something, one needs a positive vision and a plan for achieving it."
Mr Flynn and Ms McFarland complement each other, analysts say.
A retired lieutenant-general with a somewhat maverick reputation, Mr Flynn has seen close combat in Afghanistan and Iraq and ran the Defence Intelligence Agency from 2012 to 2014.
Ms McFarland in turn brings to the table a background in policy.
Among the key points in the Weinberger doctrine was the US should not commit forces to combat overseas unless the engagement was deemed vital to its national interest or that of its allies. Second, the commitment should be wholehearted, with the intention of winning - or not at all. It also should have clearly defined political and military goals.
The Weinberger doctrine sounds similar to what Mr Trump has been outlining during his campaign - an aversion to intervention overseas, but also a Reagan-era like build-up of the military, especially the navy.
"President-elect Donald Trump does not speak softly, but he clearly believes in military power - what Theodore Roosevelt called 'the big stick', " Professor Dr Eliot Cohen, of Johns Hopkins University's School of Advanced International Studies, wrote in The Wall Street Journal.
