Russia’s invasion of Ukraine and Israel’s war on Gaza are massive humanitarian crises. They are transforming the world we live in, diverting attention and resources from sustainable development and from tackling climate change. This chapter spells out the central concerns of this book and the author’s reasons for writing it. It argues that the two wars not only interconnect but also are comparable in important respects. Both are colonial wars with origins in the disintegration of empires; both are asymmetric conflicts rooted in profound inequalities; both raise difficult questions about the impunity of the states and armed actors for the destruction of human lives and crimes against humanity. This chapter spells out these and other similarities, as well as certain important differences, which are considered in more detail in the remainder of the book.