Sentence:  Rather than relying solely on the presence of violence or the threat of it by opponents of the regime, [...It was] brought about by abnormal means[. ...] Demonstrations of the sort that brought about the collapse of the communist regimes in Eastern Europe were not <WSD>normal</WSD>, and where attempts had previously been made to hold them, they were invariably suppressed by force. 
Meaning of the word marked with <WSD> tags:  According to norms or rules or to a regular pattern.