the French assumed that the Mexicans would give up should their capital fall to the enemy -- as European countries traditionally did.

Tell that to Frederick the Great. In the Seven Years' War, he twice lost Berlin to his enemies, but rallied to win the war anyway.

For that matter, the Froggies should know better. They captured Madrid in the Peninsular War, but the Spaniards fought on. They captured Moscow in 1812 (yes, I know St. Petersburg was the "official" capital then, but Tsars were still crowned in Moscow), but the Russians fought on.

This grand army smashed the Confederates at Gettysburg just 14 months after the battle of Puebla, essentially ending the Civil War.

I guess that's why 10,000 Confederate soldiers were fighting inside the city limits of Washington one year and nine days after the Battle of Gettysburg ended. I love any article that tells the tale of a French defeat, but get your facts straight.

Napoleon's French Army had not been defeated in 50 years

Who had it fought in 50 years? It's easy to be undefeated in war when you never fight.

It's not true, anyway. The French Army was defeated several times in Algeria by Abd al-Qadir during the 1830s and 1840s.