The question of how Donald Trump won the 2016 election looms over all of the many controversies that continue to swirl around him to this day. In particular, was his victory the result of Russian meddling in our political system? Up until now, the answer to that has been equivocal at best given how difficult it is to prove. Trump has vociferously denied it, as has Vladimir Putin himself. Even the famous intelligence reports establishing that the Russians interfered hold back from saying whether the interference tipped the scales in the outcome. In Cyberwar, however, the eminent scholar Kathleen Hall Jamieson, who sifted through a vast amount of polling and voting data, is able to conclude with a reasonable degree of certainty that Russian help was crucial in elevating Trump to the Oval Office. Put simply, by changing the behaviour of key players and altering the focus and content of mainstream news, Russian hackers reshaped the 2016 electoral dynamic. At the same time, Russian trolls used social media to target voting groups indispensable to a Trump victory or Clinton defeat. There are of course many arguments on offer that push against the idea that the Russians handed Trump his victory. Russia's goal was fomenting division, not electing Trump. Most of the Russian ads reportedly did not reference either the election or a candidate. Nor did they differ much from U.S.-based messaging that was already in play. Russian intervention did not surgically target Trump in key states. Finally, if WikiLeaks' releases of stolen email had truly affected the vote, Clinton's perceived honesty would have dropped in October. Jamieson, drawing from her four decades of research on the role of media in American elections, dispenses with these arguments through a forensic tracing of both Russian hackers' impact on media coverage as well as the ebbs and flows of Trump's polling support over the course of the campaign. To be sure, it is impossible to prove with absolute certainty that the Russians handed the election to Trump because there is too much that we don't know. That said, the lessons of a half century of research on the role of media framing in elections strongly suggests that many voters' opinions were altered by Russia's wide-ranging and coordinated campaign-including at least seventy eight thousand votes in three key states. Combining scholarly rigour with a bracing argument, Cyberwar shows that we can now be reasonably confident that Russian efforts helped put Trump in the White House.