Sentence:  By some paradoxical evolution rancour and intolerance have been established in the <WSD>vanguard</WSD> of primitive Christianity. Mrs. Spoker, in common with many of the stricter disciples of righteousness, was as inclement in demeanour as she was cadaverous in aspect. 
Meaning of the word marked with <WSD> tags:  The person(s) at the forefront of any group or movement.