Defend entails/necessarily involves Fight. Defend is a different concept from Attack. Attack is related to Invasion. 
Part is related to Chest. Chest is the opposite of Chance. Chance is related to Dare. 
Fight <--Entails-- Defend <--DistinctFrom--> Attack <--RelatedTo--> Invasion 
Part <--RelatedTo--> Chest <--Antonym--> Chance <--RelatedTo--> Dare 