The “Todos Los Pueblos Del Mundo Estan En Las Brigadas Internacionales Al Lado Del Pueblo Espanol” poster means “All the people from around the world are in the International Bridgade fighting alongside the people of Spain”.
The international brigades fought on the communist side during the Spanish Civil War. They were famously made up of people who travelled from around the world to support the Spanish Communist Movement. Famous writers such as Ernest Hemingway and George Orwell both fought with the International Brigades.
This poster showed the Spanish Communist supporters that the people of the world were travelling to Spain to support their cause. This improved morale amongst the people and the soldiers during a very difficult and arduous conflict.