Resistance movements during World War II occurred in every occupied country by a variety of means, ranging from non-cooperation, disinformation and propaganda, to hiding crashed pilots and even to outright warfare and the recapturing of towns. In many countries, resistance movements were sometimes also referred to as The Underground.
Among the most notable resistance movements were the Polish Resistance, including the Polish Home Army, Leśni, and the whole Polish Underground State; the Soviet partisans, the Italian Resistenza led mainly by the Italian CLN; the French Resistance, Yugoslav Partisans, the Belgian Resistance, the Norwegian Resistance, the Danish Resistance, the Greek Resistance, the Dutch Resistance and the politically persecuted opposition in Germany itself (there were 16 main resistance groups and at least 27 failed attempts to assassinate Hitler with many more planned): in short, across German-occupied Europe.
Many countries had resistance movements dedicated to fighting the Axis invaders, and Germany itself also had an anti-Nazi movement. Although Britain was not occupied during the war, the British made complex preparations for a British resistance movement. The main organisation was created by the Secret Intelligence Service (SIS, aka MI6) and is now known as Section VII. In addition there was a short-term secret commando force called the Auxiliary Units. Various organizations were also formed to establish foreign resistance cells or support existing resistance movements, like the British Special Operations Executive and the American Office of Strategic Services (the forerunner of the Central Intelligence Agency).