Happy endings in historical fiction
Taking this to its conclusion basically requires you to embrace Whig history.
In a sense the "the sequel can't undermine the happy ending" rule amounts to forcing Whig history on your fictional universe.
Only if you set the stakes absurdly high. Jane and John can live together happily ever after without the universe getting better all the time.
It seems like one way to get around this is to use an original character in the historical setting. You can have them and their loved one(s) get away to somewhere a little safer before everything goes to pot back home.
It helps. Though sometimes, such as in the War of Roses, even there there can be doubts.
Taking this to its conclusion basically requires you to embrace Whig history.
In a sense the "the sequel can't undermine the happy ending" rule amounts to forcing Whig history on your fictional universe.
Only if you set the stakes absurdly high. Jane and John can live together happily ever after without the universe getting better all the time.
It seems like one way to get around this is to use an original character in the historical setting. You can have them and their loved one(s) get away to somewhere a little safer before everything goes to pot back home.
It helps. Though sometimes, such as in the War of Roses, even there there can be doubts.