International support for a return to democracy in Venezuela has been growing since Juan Guaidó took the oath of interim president on Wednesday. The crucial but underreported question now is whether dictator Nicolás Maduro’s protectors in Cuba and Russia will intervene to stop this democratic uprising.

The Venezuelan military holds the key to whether Mr. Maduro will step down peacefully. Common sense and reporting in the country suggest that a good part of the army is ready to side with the Venezuelan people. The rank and...