Scholars say that it was the Swedish system that won the day. However looking at the battle it appears Tilly and the imperials really lost the day for reasons other than that. Especially since Tilly didn't field as many units and didn't have many reinforcements. Because of this it looks like he stretched his line out worse than what would normally occur. As well as this it looks like one of his generals being hot headed led the charge with his left flank before orders were completely given. Besides this instead of meeting Gustav at the river he waited for him which seems to have also contributed to Gustav's win. Furthermore, after this battle the Spanish system proved it was very much still versatile and viable in other battles before and after this one.

I guess I point all this out to say that I have a hard time believing the Spanish system was really truly defeated by the Swedish system. I know the Swedish system married both the best parts of the Spanish system and Dutch system along with Gustav's insight to use combined arms fire and reintroduce calvary shock value to the battlefield which had lost popularity. But even this isn't entirely accurate to the narrative as I've dug deeper it seems that others had already recognized all the developments Gustav had put into his Swedish system.

So why do we believe it was the Swedish system that won the Battle of Brietenfield?