“Sugedachi” describes a scene where a samurai joins to help his companion who is inferior in his battle. It seems that the word “sugedachi” was created from helping a company with the sword in his hand.
In the samurai drama, it refers to encouraging and assisting as there is a phrase “Let me offer sugedachi” in the sense of “helping in the revenge, fighting, duel etc.”
Recently, it seems that “sugedachi” is used to refer to cooperating with someone.