"Which has wreaked more havoc through history: a crossbow or a cannon? Now readers can find out with this installment in the Head-to-Head series that mashes up famous military weapons from throughout history. Each of the 20 subjects features a description, color illustration, and a sidebar of rankings in key categories. Friends flip to random pages and then "battle" one another in a chosen category. Covers the history of key military technology from ancient to modern times."