Last week, U.S. President Barack Obama announced two key replacements in his national security team. While the president remains the key foreign policy decision-maker, the changes constitute important shifts and could well impact his decisions. To nations like Japan, they are also a reminder of the role that women can play in national security policy.

Mr. Obama announced that Ms. Susan Rice, currently serving as U.S. ambassador to the United Nations, would replace Mr. Tom Donilon as national security adviser.

Replacing Ms. Rice at the United Nations (subject to U.S. Senate confirmation) will be Ms. Samantha Power, a former journalist who has been serving as presidential adviser on human rights and multilateral affairs. The moves were long-anticipated.