Why Talk Tough? Explaining Japanese Prime Ministers’ Proactiveness in National Defense Rhetoric

What explains variations in the proactiveness of Japanese Prime Ministers (PMs) toward national defense? Although the Japanese Constitution renounces the use of force, leaders sometimes speak assertively over national security. Drawing on competing international relations and Japanese foreign policy theories, this study seeks to quantitatively model and analyze predictors of political rhetoric in PMs’ speeches and statements from 2009 to 2019. Each statement is coded into four sets of binary dependent variables through content analysis and tested against five competing hypotheses. The main finding reveals that leaders become more likely to advocate for specifically assertive national security policy when Chinese vessel intrusion increases, but not when North Korea missile tests and aircraft scrambles increase. Instead of a diversionary use of words, an emboldening effect is evident in rhetoric that evokes responsibility in international defense, moderated by ruling government strength. The findings advance academic understandings of Japanese national security policy messaging and highlight the effect of external threat perception on political rhetoric.