This chapter covers the Mexican-American War (1846-1848) and the Franco-Mexican War (1861-1867), two of the deadliest wars in nineteenth-century Latin America. A blowing defeat, and a glorious victory, these wars set Mexico in a road to anarchy and state consolidation, respectively. The chapter starts covering early episodes of war in New Spain, like the Mexican victory against the French in the Pastry War (1838-1839), which provided initial impulse for centralizing projects. It then turns to the Texan Revolution and the Mexican-American War, and corroborates the predictions of the theory in the behaviour of all actors and on each phase of the war. Leaving Mexico in the state of total anarchy and state collapse expected after a defeat, I then take a detour to discuss how victory in the Filibuster War (1856-1857) impacted Costa Rica, providing a tentative answer for the mystery of its comparatively high political development until our day. Finally, I return to Mexico and cover the Second French Intervention of Mexico, a blessing in disguise, for the victory against the French ushered the period of more spectacular stability and growth in Mexican history.