Sentence:  there was besides, in an already dominating and growing element, a motive that was stronger and more enduring than enthusiasm —an implacable antagonism which acted side by side with the cause of the Union as a perpetual impelling force against the social conditions of the South, controlling the counsels of the government, and <WSD>cadencing</WSD> the march of its armies to the chorus:/     John Brown's body lies mouldering in the grave,/     But his soul is marching on! 
Meaning of the word marked with <WSD> tags:  To give a cadence to.