Czechoslovakia's resistance movement, like others in Europe, was split between those loyal to Stalin and those loyal to their government in exile. Like other resistance units in Europe, they played an important part in World War Two - if only for the intelligence they gathered for the Allies.
Czechoslovakia had ceased to exist when Hitler sent in his forces to Slovakia in March 1939 in defiance of the Munich Agreement. A Czech representative council had been established in London. In early 1940 it had made contact with elements of the resistance movement within Czechoslovakia and amalgamated the various units together into the Central Leadership of Resistance at Home (UVOD). Communist groups within Czechoslovakia did not join UVOD as a result of the Nazi-Soviet Pact of August 1939. However, this approach ended with Operation Barbarossa in June 1941.
Occupied Czechoslovakia had been treated as other occupied countries were - cruelly. Collaborators had helped the Germans in enforcing its authority over the Czech people. Many thousands had been deported to Germany as forced labourers, rationing gave the people the barest amounts of food and those in work had their salaries drastically cut. Reinhard Heydrich was sent to Prague in September 1941 to enforce Nazi rule. Within a few weeks, the Gestapo rounded up nearly 5000 people thought to be associated with the resistance movement within Czechoslovakia. The majority were murdered.
If anything, this action by Heydrich seemed to spur on those in UVOD. Sabotage was used with increasing success. According to German records, factory production went down by 33% during the second half of 1941. Heydrich wrote to Martin Bormann, that his attempts to put down the resistance movement in Czechoslovakia had not been as successful as he would have wished.
In May 1942, Heydrich was assassinated by two Czech agents trained and sent out by the British. It seems that UVOD did not support this move as they feared the consequences. They had good reason to do so as the villages of Lidice and Lezaky were destroyed along with their inhabitants, thousands of hostages were shot and many more sent to concentration camps. UVOD suffered badly as a result of Heydrich's assassination. It continued to operate but as separate units within Czechoslovakia. The government in exile in London ordered what remained of UVOD to operate on a “defensive basis” only.
This meant in essence the collection of intelligence for the Allies as opposed to sabotage, killings etc that were bound to result in savage reprisals. UVOD was very good at intelligence gathering and their network even collected intelligence on German operations in the Balkans and it passed on to the Allies intelligence on the V1 and V2 laboratories at Peenemünde.
The Czech communist resistance groups wanted a more direct approach. Their loyalty was to Stalin and not to the government in exile. As the Red Army advanced west and the German Army retreated, groups of Czech communist resistance fighters joined either the advancing Red Army to fight or joined Russian resistance fighters. Their work as resistance fighters also continued in Czechoslovakia itself. Russian trained agents operated in Slovakia and as the Red Army became more and more successful, these agents within Slovakia encouraged more and more people to involve themselves in an armed uprising. As the German Army started to retreat and the Red Army started to assert itself in Eastern Europe, the Czech communist resistance movement effectively dominated all the key posts in the resistance movement in Czechoslovakia. Any co-operation between the communists and other groups within UVOD ended.