In "Civil Disobedience," what war does Thoreau say made him distrust government's ability to rule justly?

Civil disobedience is the active, professed refusal to obey certain laws, demands, and commands of a government, or of an occupying international power. Civil disobedience is a symbolic or ritualistic violation of the law, rather than a rejection of the system as a whole. Civil disobedience is sometimes, though not always, defined as being nonviolent resistance.