In World War II, many governments, organizations and individuals collaborated with the Axis powers, "out of conviction, desperation, or under coercion." Nationalists sometimes welcomed German or Italian troops, believing they brought liberation from colonization. The Danish, Belgian, and Vichy French governments attempted to appease or bargain with the invaders, in hopes of mitigating harm to their citizens and economies. Some countries cooperated with Italy and Germany because they wanted to regain territory lost during and after the First World War or which their nationalist citizens simply coveted. Others, such as France, already had strong fascist movements and/or anti-semitic sentiment, which the invaders validated and empowered. Individuals such as Hendrik Seyffardt in the Netherlands and Theodoros Pangalos in Greece saw collaboration as a path to power in their country. Others believed that Germany would prevail, and either wanted to be on the winning side, or feared being on the losing one.

Axis military forces recruited many volunteers, often with promises they later broke, or from among POWs trying to escape appalling conditions in their camps. Other volunteers freely enlisted because they subscribed to Nazi or fascist ideology.

Collaboration with Nazi Germany and Fascist Italy

In France the term "collaborationist" was coined for those who collaborated for ideological reasons. Bertram Gordon, a professor of modern history, also used the terms "collaborationist" and "collaborator" for ideological and non-ideological collaboration. Elsewhere, "collaboration" described cooperation, sometimes passive, with a victorious power.

Collaboration with Nazi Germany and Fascist Italy

Stanley Hoffmann saw collaboration as either involuntary, a reluctant recognition of necessity, or voluntary, opportunistic, or greedy. He also categorized collaborationism as "servile", attempting to be useful, or "ideological", full-throated advocacy of the occupier's ideology.

Collaboration with Nazi Germany and Fascist Italy

Collaboration in Western Europe

Belgium

Belgium was invaded by Nazi Germany in May 1940 and occupied until the end of 1944.

Political collaboration took separate forms across the Belgian language divide. In Dutch-speaking Flanders, the Vlaamsch Nationaal Verbond (Flemish National Union or VNV), clearly authoritarian and anti-democratic and influenced by fascist ideas, as part of the pre-war Flemish Movement, became a major player in the German occupation strategy. VNV politicians were promoted to positions in the Belgian civil administration. VNV and its comparatively moderate stance was increasingly eclipsed later in the war by the more radical and pro-German DeVlag movement.

In French-speaking Wallonia, Léon Degrelle's Rexist Party, a pre-war authoritarian and Catholic Fascist political party, became the VNV's Walloon equivalent, although Rex's Belgian nationalism put it at odds with the Flemish nationalism of VNV and the German Flamenpolitik. Rex became increasingly radical after 1941 and declared itself part of the Waffen-SS.

Although the pre-war Belgian government went into exile in 1940, the Belgian civil service remained in place for much of the occupation. The Committee of Secretaries-General, an administrative panel of civil servants, although conceived as a purely technocratic institution, has been accused of helping to implement German occupation policies. Despite its intention to mitigate harm to Belgians, it enabled but could not moderate German policies such as the persecution of Jews and deportation of workers to Germany, although it did manage to delay the latter to October 1942. Encouraging the Germans to delegate tasks to the Committee allowed much more efficient implementation than could have been achieved by force. Since Belgium depended on Germany for food imports, the committee was always at a disadvantage in negotiations.

The Belgian government in exile criticized the committee for helping the Germans. The Secretaries-General were also unpopular within Belgium itself. In 1942, journalist Paul Struye described them as "the object of growing and almost unanimous unpopularity." As the face of the German occupation authority, they became unpopular with the public, which blamed them for the German demands they implemented.

After the war, several of the Secretaries-General were tried for collaboration. Most were quickly acquitted. , the former secretary-general for internal affairs, was sentenced to twenty years imprisonment, and Gaston Schuind, Judicial Police of Brussels, was sentenced to five. Many former secretaries-general had careers in politics after the war. Victor Leemans served as a senator from the centre-right Christian Social Party (PSC-CVP) and became president of the European Parliament.