The Soviet Union may have easily been considered a "silent partner" of the Axis at the time. It was never a signatory to the Pact of Steel (the original "Axis Pact"), and obviously inimical to the Anti-Comintern Pact. Yet its relationships with Nazi Germany were – at least at the surface – more friendly than either country's with the US. The USSR had joined Germany's September 1, 1939, invasion of Poland in mid-September, and the countries had treaties of economic assistance and cooperated in military research. However, just one month before "I'll Never Heil Again" was released, Germany invaded the Soviet Union.