In nineteen hundred and forty nine, the USA got very wise.
It found a country had crossed the line, had an atom bomb of the very same kind!
People got worried, across the land, just like folks got in Japan..."
The Warsaw Treaty of Friendship, Cooperation and Mutual Assistance, better known as the Warsaw Pact in the West (it used to be known as the Warsaw Treaty Organization too, but that name has now disappeared due to a more famous organization taking the acronym), was a military defense alliance of the USSR and its European satellite states. It was pretty much formed as a direct response to NATO.
Accordingly, it's a good place for us to discuss Central and Eastern Europe as Commie Land.
One should not treat the entirety of the Soviet bloc as the same thing. There were many differences in policies and repression levels, both between countries and within the same country at different times (sticking dissidents in mental hospitals was pretty common though).
Very important note: Yugoslavia and Albania don't count. They were part of Commie Land, but not the Warsaw Pact. Yugoslavia was never a member and Albania finally left over the Prague Spring. The latter aligned for some time more with China.
The states of the Warsaw Pact were:
Officially, the countries were not supposed to intervene in each other's internal affairs. Interventions in Hungary (1956) and Czechoslovakia (1968) were justified under "requests by the local governments".
With Hole in Flag, the Warsaw Pact collapsed.
In fiction, the existence of Warsaw Pact members other than the Soviet Union and East Germany is often ignored. Especially in Spy Dramas. Commie spies will almost invariably be Russian. Their home country will nearly always be depicted like Russia. You won't see the warm, almost-Mediterranean climate of southern Bulgaria, nor the medieval architecture of Prague (unless it's meant to be a crossover with Überwald).
In case of World War, break glass
For most of the Cold War, the conventional military balance in Europe was in favor of the Warsaw Pact from the 1950s to the late 1980s, a imbalance which was off-set by NATO's nuclear superiority until the Soviets achieved rough parity in the late-60s. From the mid-80s on, the introduction of various emerging "information age" technologies for military use swung the balance to the West. The plans for World War III were to go on the offensive immediately, in case of attack. The Warsaw Pact never planned to strike first. Neither did NATO for that matter. This meant that a Third World War could only have been started by accident. But neither side knew this, and often assumed that the other was preparing to strike first.
WP equipment was virtually all Soviet or local copies of Soviet weaponry (notable exception- the Czechoslovak L-39 trainer aircraft series. Remember the beginning of Tomorrow Never Dies? That one). When these countries later joined NATO, the U.S. had some MiGs and Sukhois to play with. Most of these states are now slowly retiring their Soviet-made aircraft.
A lot of works called into question the reliability of the non-Soviet Warsaw Pact members in an offensive war against NATO. The general answer would be as long as the Soviets were successful, the loyalty of the Warsaw Pact nations would certainly be assured. Even then, the Soviets would had to take some measures to avoid the Pact from unreliability, like not having East Germans fight West Germans, having Poles fight British or American troops, and using a Soviet formation in between two Pact armies.
For those interested in that subject read this PDF, which contains a transcript of a conference where former senior officers from both sides discuss their war plans with each other. Additionally, one can also read some interviews here to see the perspectives from Soviet officials, including members of the USSR General Staff.
The Warsaw Pact and its member states in fiction:
As Commie Land, all the states turn up at some point.
- Superman: Red Son had the Soviets publicly announce his existence using the intro from the radio and tv series with one natural substitution: "the American way" was replaced with "expansion of the Warsaw Pact".
- From Russia with Love had some Bulgarian DS agents preforming counter-espionage on MI-6's Istanbul division for the Soviets.
- The first third of The Living Daylights was set in Bratislava, Czechoslovakia (doubled by Vienna, Austria) and featured incursions with the Czech police and army.
- In Red Storm Rising, bar a small appearance from GDR forces pre-war, the non-Soviet forces are ignored.
- In Clancy's Red Rabbit, however, other Pact nations are pointedly not ignored. The Soviets subcontract their assassination plot to the Bulgarians, and a KGB officer has to go to Yugoslavia (yes, not actually a Warsaw Pact nation) to defect.
- In Red Army, DDR, Polish and Czech officers attend Malinsky's front briefing, but only East German forces play a minor role subordinate to Starukhin's Third Shock Army.
- Several episodes of MacGyver have Mac treading the territory of WP countries. A notable one involves Mac trying to smuggle out a dissident from Czechoslovakia's capital of Prague.
- It is a card event in Twilight Struggle. It's existence usually dissuades US forays into Eastern Europe until it is played, and is one of two cards that allows "NATO" to be played (the other being "Marshall Plan").
- East Germany, Czechoslovakia and Poland along with the Soviet Union are playable sides in Wargame: European Escalation.
- The same applies to the Cold War installment of the Steel Panthers series, where the smaller Warsaw Pact countries even have some unique units and specialties of their own in addition to Soviet-supplied military equipment.
- Surprisingly averted in World in Conflict, despite it being a Cold-War era strategy game. In fact, the fighting on the Central Front is almost completely ignored, except for tangential references in briefings.
- An East German tank regiment shows up in the Flashpoint Campaigns scenario A Thin Tan Line, where they attack a British battalion defending an important town. Czechoslovak troops will appear in the upcoming entry Southern Storm.