Spanish Civil War 1936-9 - Following an army coup against the government, the Nationalists (army, Church, conservatives) fought the Republicans (socialists, republicans, anarchists, communists). Germany and Italy supported the Nationalists whereas the USSR supported the Republicans. Britain and France were 'neutral', insisting on arms embargoes. However, even after agreeing to the embargoes, Germany and Italy continued to support and fight for the Nationalists.
With the gradual defeat of the Republicans, the Soviets were more convinced that Britain and France believed more so in preserving their own security rather than collective security (Spain belonged to the League of Nations). Britain and France were also understood to oppose communism (USSR) more so than fascism (Germany), as such, they could not be depended upon to form an alliance against fascism.
Germany for the most part supplied Nationalists with supplies, with minimal military participation (e.g. German-piloted aircraft).
Germany's main goal was to prolong and extend the Civil War in the hopes that this would trigger France's eventual involvement, which would draw out its resources and remove its military presence along the Franco-German border. This could also weaken France diplomatically. (though France ultimately did not interfere)