Bartoletti proposes a new theory for wars with a high participation of great powers since the 1490s (curiously excepting World War II but including an equally curious possible future India/Russia encirclement of China). If geographical circumstances inflict two great powers as neighbors, the encircled great power is likely to strike first at one of them, especially if the target improves its invasion capability. Alliances, bloc polarization, and contagion ensure that other great powers will join in. The theory is parsimonious and appears to be supported by case studies. The main problem is the very strong assumptions at the foundation for the theory. We live in separate IR theory silos or perhaps bunkers. If you like your theoretical bunker to be constructed based on elevating anarchy over hierarchy, enshrining survival as essentially the exclusive goal of decision-makers, regard all great powers as equal in capability and ignore the ones that are not land powers, view security dilemmas as both rampant and helpful to explaining conflict, and do not mind cherry picking dates for major power warfare (for instance, the Italian wars in this book were fought 1521–59 and the Thirty Years War 1635–48), Bartoletti's theory may be appealing. If you have strong reservations about any of these assumptions, the theory will be less compelling. Two-front wars certainly have a role to play in the etiology of major power warfare. But you have to be willing to overlook a great deal to argue that they are the key to understanding major power warfare. For example, had there been no Franco-Russian alliance in 1914, is it impossible to imagine World War I breaking out?