The International Brigade was not formed to protect freedom and democracy. It was founded as a tool of of the Comintern, to promote the interests of the Soviet Union - and thereby of Joseph Stalin, the butcher of millions. It made political sense for the International Brigade to recruit non-communists - useful fools was what Lenin had called such people in an earlier manipulation of gullible decency - but of course most were then vetted by the NKVD, the Soviet Union's secret police.