The "shifting" of "human relations" that Woolf uses to help explain Modernism is embodied by the First World War.  The fundamental premise of the movement was to express this "shift" or seismic change in that way through which individuals and human beings work with one another.  World War I was one such change.  The war fits into Modernism because it transformed so much in terms of human relations.  Human beings no longer held out much in way of hope in terms of the level of cruelty that can arise.  The horrors of the war did much to dispel a hope of redemption within human beings.  The human trust in government and institutions that gave their consent and zealous support to the war effort also dissipated as a result of the First World War.  At the same time, there was another shift in the way which technology was perceived.  No longer could it only be seen as a way to make life better, as it was coopted to become a more "efficient" way of killing millions.  The war's lasting effect was one of despair and disillusion, contributing heavily to both the pall that existed over Europe in its wake and the Modernist movement that resided so much the reality of the war.