Translation of an historical turn of phrase?

As there are some Spanish contributors here with a knowledge of Spanish history I am taking the opportunity to try and solve a problem that still plagues me.

I am trying to translate a document from the Archivo General de Simancas written in 1649. The author uses the phrase 'enemigos de la fee'. I think this must be a saying of the period which does not translate into anything intelligible in modern Spanish usage.

What would 'enemigos de la fee' mean in 1649.

Any helpers?

I didn't find the right solution from the internet.
References:
http://hist orum.com/european-history/127822-translation-historical-turn-phrase.html
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