Sentence:  The only contrary action , in the future as in the past , <WSD>runs</WSD> the risk of war ; and , now and in the future unlike in the past , any attempt to repel injury and to preserve any particular civilized attainment of mankind or its provisional justice runs some risk of nuclear warfare and the danger that an effect of it will , by human action , render this planet less habitable by the human race . 
Meaning of the word marked with <WSD> tags:  take a risk in the hope of a favorable outcome