We compare political mobilization and support for democratic values during the French Revolution among the home bailliages and among individual members of French regiments sent with the Comte de Rochambeau to fight alongside American revolutionaries (1781-83), to others also assigned there who failed to arrive due to logistical failures and British blockade. We provide evidence for revolutionary contagion: bailliages with 10% more Rochambeau veterans were 6.4% more likely to submit grievances to the King that were “Most Strongly Democratic” in 1789. They mobilize political clubs earlier, are more likely to engage in revolt and as individuals were more likely to show loyalty to moderate democratic revolutionary reforms both within the army and the National Assembly. Other veterans mobilize too, but less so and not for democratic principles. Similarly, exposure to Enlightenment ideas has limited effects absent American veterans. We interpret these results as reflecting the complementarity between exposure to democratic ideas and organizational skills of veterans in generating contagion between two of the world’s great revolutions.