I know that by definition, 'triumphant' is an adjective and 'triumphantly' is the adverb form, but I've seen usages like the following sentence:
Napoleon returned triumphant to France after the war he fought and won in Italy
Here, the term 'triumphant' is being used as an adverb. I know by grammar, adjectives cannot be used to enhance verbs, but I've also heard about exceptions where general grammar doesn't work. I'm not sure whether this would be one of the exceptions.
Now, is this usage correct?