Explanation: During the Second Punic War, the Carthaginian general Hannibal quite soundly defeated several Roman armies that were sent after him in Italy. In fact, so many Romans died that it's estimated that 20% of Rome's military-age males were killed by Hannibal. For reference, WW1 had about 15% killed before the will to fight collapsed and the war ended.
And yet, Rome kept coming back, with more and more and more men. They banned mourning. They taxed all luxuries. They called up all the young men they could regardless of social class. They armed slaves in exchange for their freedom. Whatever it took. And because of that determination, Rome eventually, resoundingly won the war, despite losing entire armies to Hannibal's forces.