When historians look back at the 2016 election, they will likely determine that it represented one of the most successful information operation campaigns ever conducted. A foreign power, through the targeted application of cyber tools to influence America’s electoral process, was able to cast doubt on the election’s legitimacy, engender doubts about the victor’s fitness for office, tarnish the outcome of the vote, and frustrate the president’s agenda.

Historians will also see a feckless Congress—both Democrats and Republicans—that...