Recent history your characters are all likely to know! Well, at least to some extent.
Given that the War(s) happened just shy of two hundred years ago, they’re rather shrowded in myth and simplified retellings, but since they were also the least really big brouhaha to hit europe, and installed the current system of government, they’re still required reading.
Short version: Italy was going on an empire building binge, and had conquered France Sud, a few other surrounding countries, and was well in the process of taking over Anglo France, when to all reports Kayz DeWildar appeared out of nowhere, and somehow managed to marshal a small number of militia men and refugees into a military force that beat back the armies of the Italian King, reclaiming not just Anglo France, but France Sud as well. And then Belgium. And then the other Powers of Europe became afraid of this mysterious juggernaut, and declaired war.
Kayz Allied with the Dog King(at the time a moderately powerful warlord), and his army took on all comers over the next decade or so, including a few preemptive attacks, and even took a few preemptive surrenders.
When all the dust had settled, and all the treaties been written, Kayz was at least nominally in charge of most of Europe, and has very agreeable treaties with most of the bordering states.
And thus is the quick(and relatively clean) version of what happened int he sentile wars.