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:
Dissolution_of_the_Soviet_Union

Context:
In a new and effective tactic, the Popular Front launched a rail blockade of Armenia, which caused petrol and food shortages because 85 percent of Armenia's freight came from Azerbaijan. Under pressure from the Popular Front the Communist authorities in Azerbaijan started making concessions. On September 25, they passed a sovereignty law that gave precedence to Azerbaijani law, and on October 4, the Popular Front was permitted to register as a legal organization as long as it lifted the blockade. Transport communications between Azerbaijan and Armenia never fully recovered. Tensions continued to escalate and on December 29, Popular Front activists seized local party offices in Jalilabad, wounding dozens.

Question:
What did the Popular Front do to Armenian railways?

blockade