Hannibal of Carthage ranks as one of the most successful generals ever to lose a war. He invaded ancient Rome and by brilliant stratagems destroyed one Roman army after another - all to no avail. The Romans kept producing new armies, and Hannibal was ultimately forced to retreat back to North Africa where, years later, he chose suicide over submission to Rome.
The Romans did not defeat Hannibal on the field. Instead they defeated him in the nursery. The matres and patres of the eternal city begat larger litters than the Carthaginians or Greeks or any other ancient peoples they had to contend with. Demographics turned out to be destiny.