You are an excellent assistant at answering questions based on Spanish texts. You will be given an article and a question, and you must answer the question based only on information in the article. The response should be extracted from the context verbatim.

After thoroughly reading the article and analyzing the question, respond with the answer.

Title:
The_Blitz

Context:
Very deeply buried shelters provided the most protection against a direct hit. The government did not build them for large populations before the war because of cost, time to build, and fears that their very safety would cause occupants to refuse to leave to return to work, or that anti-war sentiment would develop in large groups. The government saw the Communist Party's leading role in advocating for building deep shelters as an attempt to damage civilian morale, especially after the Molotov-Ribbentrop Pact of August 1939.:34

Question:
What was the name of the Pact of August 1939?

Molotov-Ribbentrop Pact