Theres a novel by Poul Anderson called The High Crusade, which has an alien spacecraft land in rural England in 1345 during the Hundred Year’s War. The local baron has been raising an army to help King Edward against the French, and immediately assumes this must be some kind of enemy trick.
In a way, he’s correct: the aliens are scouts for a brutal and repressive interstellar empire, which has dominated numerous planets through their devastating technology.
Unfortunately, this reliance on advanced weapons means they’ve completely forgotten all forms of melee combat and Sir Roger of Tourneville leads his militia to defeat the aliens easily.
They spare a single enemy, forcing him to fly the ship at spearpoint. They intend to raid behind enemy lines, capture the king of France to end the war, and then go onward to reclaim the Holy Land using the same tactic.
In an attempt to outwit the knights, the alien pilot actually travels to the nearest Imperial planet, where he expects the occupying military forces to save him.
I won’t spoil the details, but the knights accept this as a challenge and declare the launch of the “high crusade”.
That last picture is so stupidly badass I might tattoo that next to my dick cause it ain’t getting any better after that