The Nazis were known for, among other things, their propaganda.
But this wasn't something that started during the war, it had been going on ever since the Nazi Party was established in 1923, and picked up even more when Hitler became Chancellor in 1933.
One thing the Nazis did a lot of was hold rallies, including one annually in Nurenberg. The Germans called these rallies 'Reichsparteitag,' which translates to 'National Party.'
They used these rallies to help gain support for German citizens, while showing off their abilities to organize and to show the rest of the world that Germany was returning to full strength for the first time since World War I.
Each of the rallies had its own theme, and the theme of the rally scheduled in 1939 was "Rally for Peace." This sounds misleading, as we all know what happened over the next 6 years, which saw millions of lives destroyed. Not too unbelievable, the rally was cancelled shortly before it happened.
The reason was later found to be because the rally was scheduled for September 2, and the Nazis were planning on invading Poland on September 1.