What is the disturbance referred to on page 4?
I do not think I have the same edition of the book that you do, because the word "disturbance" is not on page 4 in my book. However, in Chapter 1, we see the following phrase used, and I think it is the one you are asking about.
Simon would have regarded with impotent fury the disturbance between the North and the South, as it left his descendants stripped of everything but their land...
In this case, you should be able to figure out what the disturbance was given the fact that the author refers to the North and the South. This is clearly a euphemistic way of referring to the Civil War. This makes sense given that many Southerners lost most of their possessions during the war.