The Spaniard Armado is a not so subtle dig at the recently defeated (by the English) Spanish Armada

Some believe, as does Asimov, that Berowne is meant to evoke Armand de Gontaut, Baron de Biron, a friend of Henry of Navarre (known in England because of his work with the army of the Earl of Essex, which supported Henry of Navarre)

[btw, the name is pronounced "bahROON" like it rhymes with "moon" (as it does in the play), not "berOWN"]

Some believe, as does Asimov, that Longaville is meant to evoke the Duc de Longueville, one of Henry's generals

This is a Biblical name, but not one ANY parent would use to name a child: it comes from the apocryphal (and Catholic) Book of Judith.  Holofernes was an Assyrian general who invaded Judea; he was killed by the titular Judith.