How did Steve get the patch? What injury did he sustain?

bo brady and patch got in bad fight over a woman named britta , sad but true but it happened years ago, when patch was in the merchant marines.bo and steve fell for the same woman which was a spy.and bo and patch even got tattoos thinking they were bonded, only to find out they were secret messages for britta ,they were best of friends before that,,im glad they are friends now.