Gloria.TV states that "the foreign knight,...Richard of York" fought, and was killed, at the Battle of Grunwald (Tannenberg) in 1410. I can find no one from the house of York who might have been at Grunwald. The elder Richard, 3rd Earl of Cambridge and son of Edmund of Langley, 1st Duke of York, was beheaded in 1415 for conspiring against Henry V, and Richard's son, Richard Plantagenet,3rd Duke of York was not born until 1411. This latter Richard was of course the father of Edward IV and Richard III. None of these men would have been able to have been at Grunwald in 1410. Does anyone know to whom the article about Grunwald is referring?
When someone is described as "Name of Place" in a medieval document that means one of two things:
1) That the person is the ruler of that place, with the appropriate title ranging from lord to emperor.
2) That the person is in someway connected to that place. For example, he might be in some senses "from" that place. For example, English prince John of Gaunt, Duke of Lancaster (1340-1399), was not the ruler of Ghent in a foreign land, but was "of Ghent" because he was born there while his parents were on business there.
So was "Richard of York" a member of the York branch of the Plantagenet dynasty, or was he merely "Sir Richard" (surname unmentioned) "of York" because he was from York?
I have found no record of a "Richard of York" who died in 1410 in the genealogy of the House of York.
Of course Richard of Conisburgh, Earl of Cambridge,(1375/76-1411) would have been about 34 or 35 at the time of the Battle of Grunwald in 1410. It is possible that he was at the battle, survived it, and was reported killed in error.
But to me it seems more probable that the report of a Richard of York killed at Grunwald in 1410, if a medieval record, refers to a knight named Richard who came from York.
The only reference to a Richard of York fighting in Grunwald I could find was from Poland: A Novel, a 1983 novel by James A. Michener (the gloria.tv article seems to be largely similar to that source, although not a direct quotation).
As the author states in the introduction to the book:
This book is a novel. (...) Most of the characters on whom the action of the novel depends are also fictional.
This, to me, suggests that Richard of York along with other foreign knights mentioned in the passage are author's creations rather than historical figures.