Let's face it, in nearly every Regency novel The Napoleonic War is mentioned. Some center entirely around a battle. And heroes. Every battle needs a hero. Every Regency Romance needs a hero!
The Battle of Copenhagen saw Vice-Admiral Horatio Nelson lead the main attack. This is where he's supposed to have disobeyed Admiral Sir Hyde Parker's order to withdraw by holding the telescope to his blind eye to look at the signals from Parker. Yes and no. Let's face it, it makes Nelson a hero in the eyes of the people even if Parker's signals gave permission to withdraw at his discretion. Nelson didn't happen to want to withdraw. His action in proceeding resulted in the destruction of many of the Dano-Norwegian ships before a truce was agreed.
How do I know so much about this battle? Bernard Cornwell's Sharpe Series. I've read every book but the final one. I'm hesitant to read that last one because it's the last one. You know how it goes. Because then it'll be the end, and the final book is about Sharpe's daughter. I want to read it, but can't quite bring myself to read the end of a series I've loved so much.
In my Regency Menage Tales, I've used the Napoleonic War in 2 separate stories, one where the men have returned from war physically undamaged and yet emotionally conflicted: Covet has he Grayson and William finally realizing their love for each other as well as the woman they both left behind, Charlotte. But in Seduction of a Proper Lady, Ethan is physically burned and both shunned from society and oddly embraced for his heroic efforts in defeating Napoleon.
Either way you look at it, The Napoleonic Wars had as much to do with the Regency Era as Jane Austen.