The War in Paraguay

In the late 20s, Bolivia starts sniffing around this region in northern Paraguay called the Chaco. Bolivians are like, well, the last time Paraguay went to war, it didn't go good. And so they're like, let's go invade and take this from Paraguay. This is going to occur in like the early 1930s. The Bolivians put an old German man in charge of their military. Now! What time?