Book excerpt: Blood and Concrete: 21st Century Conflict in Urban Centers and Megacities provides a foundation for understanding urban operations and sustaining urban warfare research. This Small Wars Journal (SWJ) Anthology documents over a decade of writings on urban conflict. In addition to essays originally published at SWJ it adds new content including an introduction by the editors, a preface on "Blood and Concrete" by David Kilcullen, a foreword "Urban Warfare Studies" by John Spencer, a postscript "Cities in the Crossfire: The Rise of Urban Violence" by Margarita Konaev, and an afterword "Urban Operations: Meeting Challenges, Seizing Opportunities, Improving the Approach" by Russell W. Glenn. These essays frame the discussion found in the collection's remaining 49 chapters. Blood and Concrete continues the legacy of Small Was Journal's coverage of urban operations, conflict and combat.