As an American, I was always taught that places like East Germany and Czechoslovakia were one-party dictatorships under communism. Strictly speaking, this is not true. To take the East German example, the government was technically a coalition of five parties that made up the "National Front." Wikipedia tells me that membership in some of these parties numbered over 100,000.
My questions are: what role did these parties play in their society & government? Were they merely puppets? How did the leaders & membership perceive themselves? How were they perceived by others?
In Czechoslovakia, there certainly were other political parties than the Communist Party of Czechoslovakia, but they were all puppets under direct control of the ruling regime and provided nothing but the illusion of political plurality, with all permitted political entities being grouped in something called the National Front. The situation was similar in East Germany or Poland, but I will leave those countries to others.
The origins of the National Front can be traced back to the Second World War. Especially with the Munich betrayal still fresh in memory of the people, the 'pro-western', to put it in simplified terms, exile government under president Edvard Beneš was always going to be in a precarious position.
In fact, as the war drew to the close it became clear that it would never wield enough power to simply return the country to its pre-war state. The pro-soviet camp was the chief political entity with the backing of the Soviets, and Beneš was forced to several concessions to maintain friendly relations with them in hopes of preventing direct Soviet action or a communist coup after the war.
In late March and early April 1945, the two sides met in Košice, modern day Slovakia, to agree on something called the Košice statute or programme. What the Beneš side had hoped to be a joint effort between the two sides aimed at maintaining Czechoslovakia turned out to be basically another shift of power into the hands of the communists, with most of the documents being prepared days in advance in Moscow.
One of the results of the Košice meeting was the establishment of a political coalition that would govern post-war Czechoslovakia – the National Front. Only the parties represented in it would be allowed to be a part of the government. It was not yet the monolithic block it would become after the events of 1948, but already in 1945 it was under the influence the communists, much like most of the Czechoslovak politics at that time.
After the communist coup of 1948, the National Front became nothing more than a front. The Communist Party of Czechoslovakia seized all power, absorbsed some elements of the Front, and made other parties undergo pro-communist or socialist reforms and purges. Understand that virtually all positions of power came to be dominated by the communists or their sympathizers. In fact, several originally non-political entities were also incorporated into the National Front, from women's unions to youth organizations.
There were other parties than the communists, some in fact with several thousand members (the People's Party had over sixty thousand registered members in the eighties), but they were all under direct control of the ruling regime. Short of submitting a blank vote, there was no way of not voting for the communist led parties with only National Front candidates available, and even then the candidates from these puppet parties would not be represented in significant numbers.
For all purposes, countries like Czechoslovakia were indeed communist dictatorships. Strictly speaking there might have been more than a single party, but they were all controlled by the Party.