Philipp Ruch's new book argues that the 1929 Wall Street crash cannot explain the Nazi breakthrough at the 1930 Reichstag election because unemployment's full force didn't arrive in Germany until July 1931. A letter from historian John Plowright, writing from Repton, Derbyshire, dismantles this claim by pointing out that unemployment more than doubled between 1928 and the 1930 election — a massive labour market shock well before Ruch's proposed timeline. Ruch's secondary argument — that regions with high unemployment actually voted less for the Nazis — is not disputed by Plowright. The data on that is reasonably well-established in the historiography. But Plowright identifies the interpretive failure: Ruch treats unemployment as a direct variable (suffering → Nazi vote) rather than an indirect one operating through a second channel entirely. That channel was fear of communism. Rising unemployment fuelled the growth of the KPD (Communist Party of Germany), which was the other great political beneficiary of the crash alongside the NSDAP. As unemployment climbed, the KPD grew. As the KPD grew, the Nazi party positioned itself as the only force with both the resolve and the paramilitary muscle — the brownshirts — to prevent a communist seizure of power in the streets. This is a causal chain with an extra link: unemployment → KPD growth → fear of communist revolution → Nazi vote as counter-revolutionary insurance. The regions where unemployment was highest may have voted KPD directly, which is consistent with Ruch's data. But the nationwide perception of communist threat — visible in street violence, red banners, and KPD electoral gains — radiated outward and drove middle-class and rural voters toward the Nazis in regions where unemployment was lower but fear was high. Plowright's most pointed observation is his last: the KPD "proved a damp squib." The communist revolution never came. But the fear it inspired was genuine, strong, and very widespread. Hindsight bias — knowing the KPD never took power — makes it easy to dismiss this fear as irrational. At the time, it was the dominant political emotion in much of Germany, and the Nazis exploited it with precision. This exchange illustrates a recurring pattern in political historiography: the temptation to find a single clean variable (unemployment, economic collapse, charismatic leadership) that explains a complex political realignment, and the corrective reminder that political behavior operates through perception and fear as much as through material conditions. The mechanism matters more than the correlation. The letter is a compact masterclass in reading historical data carefully. The numbers Ruch cites may be accurate. His causal model is what fails.
